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University of Illinois Library 


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APR 2.6 199 


L161—H 41 


LIQUID AIR 


f 23) BBS BY mG = 


LIQUEFACTION OF GASES 


Tab Ohiee Wie hy: DIOGKAPHY 
PRAGHICAL ACELICATIONS 
MANUFACTURE 


BY 


Ee Ci CONGR SLOAN bore. Db. 


ILLUSTRATED 


NEw YORK 
NORMAN, Wee HENLEY ~& CO, 
132 NASSAU STREET 


1899 


COPYRIGHTED 1899 . 
BY 
NoRMAN W. HENLEY & Co. 


COMPOSITION, ELECTROTYPING AND 
PRINTING BY 
MaACGOWAN & SLIPPER 
NEW YorK, N.-Y:, U.S. A. 


mn) 


APTOS BDI 


es S es | 2 Fp 


gE 


PREFACE. 


In- Gulliver’s veracious account of his travels we 
read of the work done in the famous Academy of 
Logado. In one department fifty men were at work 
under the superintendence of the universal artist, 
as one of the illustrious investigators was called. 
These men were engaged in various occupations. 
‘Some were condensing air into a dry tangible sub- 
stance by extracting the niter, and letting the aque- 
ous or fluid particles percolate.” So says the great’ 
Dean, selecting the solidification of air as one of the 
impossibilities worthy of embodiment in his sarcastic 
romance. 

During the present generation the triumphs in 
natural science have been most wonderful. The 
prosaic narration of what has been done sounds like 
the romancing of a Cyrano de Bergerac. We read 
of the hardest metals, such as iron and nickel, car- 
ried off in the gaseous state by carbon monoxide ; 
the surgeon uncgncernedly has the interior of his 
living patient’s body photographed ; the triumphs of 
chemical synthesis culminate in the production on 
the scale of manufacturing industry of a hydrocarbon 
from coal and water; Marconi follows a yacht race 
and telegraphs its phases to the distant shore over 
miles of water, without a wire; and to-day air is 
liquefied by the gallon, hydrogen and helium suc- 
cumb to intense cold, becoming mobile liquids, and 


ECO 
par 22 a4 ee, Ae 


PREFACE. 


the last miracles of science may figure among her 
greatest. 

The present work aims to tell the history of the 
liquefaction of gases, wherein the physicist has ex. 
ceeded the fictitious achievements told of in Gulli- 
ver. The subject, extending overa century, is full 
of interest from the biographical as well as scientific 
standpoint, and it is hoped that the presentation of it 
with such scope will be acceptable to the reader. 

For assistance in the compilation the author’s 
thanks are due to many. His requests met with 
quick response from such men as L. P. Cailletet, 
Henri Dufour, Charles E. Tripler and James Dewar. 
And a personal friendship brought about by this book 
has fully justified the labor of writing it—the friend- 
ship of that wonderfully endowed scientist Raoul 
Pictet, one of the fathers of liquid air, poet, musi- 
cian, physicist, chemist and mathematician—a verit- 
able Admirable Crichton. 

The work is but begun, the future possibilities are 
great, and it is impossible to foresee the impending 
developments in the liquefaction of gases. 


LAB EE Or CONLEN Ts. 


CHAPTER I.—Puysics. Pages 9-36 


What is liquid air?—The three states of matter: Solid, liquid and gaseous— 
Relations of pressure and heat to state assumed by matter—The critical 
state and its phenomena—Natterer’s tube—Physical units—Space, mass 
and time—Force and energy—Conservation of force an abandoned doc- 
trine—Conservation of energy—Work a synonym for development of 
energy—Waste of energy and entropy—Possibility of utilizing the lower 
forms of energy of the universe. 


CHAPTER II.—HEat. Pages 37-58 


Heat and its measurement—Thermometers—The zero point—The Celsius or 
Centigrade thermometer scale—Fahrenheit’s thermometer scale—The abso- 
lute zero—Its basis—Coefficient of expansion of gases—Determination of 
temperatures in the liquefaction of gases—Different liquids used in filling 
thermometers—The air thermometer—The hydrogen thermometer—De- 
tails of its construction—Klectrolytic hydrogen—The hydrogen or air 
thermometer formula—The thermo-electric thermometer—Onnes’ instru- 
ment and details of its construction—Its calibration—The electric resist- 
ance thermometer—Calorimetric determination of temperatures. 


CHAPTER III.—HEAT AND GASES. Pages 59-84 


The perfect gas—The ultra-perfect gas—Energy expended in heating a gas— 
Specific heat at constant pressure and at constant volume—Atomic heats 
and variations of same from equality with each other—Adiabatic and iso- 
thermic expansion of gases—Carnot’s cycle—The perfect heat engine— 
Available and unavailable energy—Unavailable energy rendered available 
by liquid air—Latent heat of melting, of vaporization, of expansion—Boil- 
ing a cooling process—Expansiona cooling process—The spheroidal state 
—The Crookes layer—Experiments and illustrations—Utilization of the 
spheroidal state in low temperature work and in liquid air investigations. 


CHAPTER IV.—Puysics AND CHEMISTRY OF AIR. 
Pages 85-91 
The atmosphere as an ocean—What air is—Its constituents—Relations of air 
to living beings—The chemist’s and physicist’s view of air—Its constancy 


of composition—Carbon dioxide—Oxygen—Nitrogen, argon and other con- 
stituents. 


TABLE OF CONTENTS. 


CHAPTER V.—THE RovaL INSTITUTION OF ENGLAND. 


Pages 92-99 

The Royal Institution—Its origin and objects—Count Rumford—Sir Humphry 

Davy—The Pneumatic Institute—Davy’s experiments in inhaling poison- 

ous gases—His engagement as director of the Royal Institution—His 
views on the utility of liquefying gases. 


CHAPTER VI.—MIcCHAEL FARADAY. Pages IOI-I1I5 


Michael Faraday--His early life—Early devotion to science—His introduction 
to Humphry Davy—Attendance at scientific lectures—Engagement at the 
Royal Institution—Injuries from explosion in the laboratory—Kuropean 
tour with Davy—Rivalry of scientific men—Davy and Faraday as rivals— 
The liquefaction of chlorine—Davy’s share in the experiment—Davy’s 
opposition to Faraday’s election as fellow of the Royal Society—Dr. Paris 
and the liquefaction of chlorine—Faraday’s descriptions of his liquefac- 
tions—Explosions—Northmore’s priority published by Faraday—Notes on 
Faraday’s liquefaction of gases—His exhibit’on of Thilorier’s apparatus— 
His later work in liquefying gases—Discovery of the magnetism of oxygen 
gas—His death—Bent tubes as used by Faraday—Experiments with use of 
bent tubes—The Davy-Faraday Laboratory. 


‘CHAPTER VII.—EARLY EXPERIMENTERS AND THEIR 
METHODS. Pages I16-151 


Perkins’ claim to have liquefied air—Its absurdity—Northmore’s liquefaction 
of chlorine—Rumford’s experiments as commented on by Faraday—Bab- 
bage’s experiment in a drill hole in limestone rock—Monge and Clouet’s 
alleged liquefaction of sulphurous oxide—Faraday’s liquefaction of chlo- 
rine—Stromeyer’s liquefaction of arseniureted hydrogen—Faraday’s bent 
tubes for liquefaction of gases—Manometer for use with them—Experi- 
ment in a straight sealed tube on the liquefaction of chlorine—Davy’s sug- 
gested method—Cagniard de la Tour—His bent tube experiments—D. Col- 
ladon—His apparatus as still preserved—Thilorier—His discovery of solid 
carbon dioxide—A fatal explosion—The improved Thilorier apparatus— 
Johann Natterer’s apparatus—His experiments—Loir and Drion’s solidifi- 
cation of carbon dioxide—Thomas Andrews, of Belfast. 


CHAPTER VIII.—Raovut PIcrer. Pages 153-171 


The life of Raoul Pictet—His education—His ice machines—Disputed priority 
—Honors awarded—His apparatus for liquefying gases—Description of its 
operation—Temperatures of the cycles of operation—His dispatch of De- 
cember 22, 1877, to the French Academy—Regnault’s statement—Hydrogen 
—His dispatch of January 11, 1878, to the French Academy - Olszewski’s 
comments on the hydrogen experiment—Pictet’s arrangement of pumps— 


~ His desire to produce liquid oxygen in quantity—Comments on his work — 
. The liquide Pictet. , 


CHAPTER IX.—Louis-PavuL CAILLETET. Pages 173-202 


The life of L.-P. Cailletet—His education—Honors received—His modification 


TABEEOF CONTENTS. 


of Colladon’s apparatus—Accidental liquefaction of acetylene by release— 
Description of his apparatus—How the apparatus was filled—The full appa- 
ratus with hydraulic press—Liquefactions of nitrogen oxide—Of carbon 
monoxide and oxygen mixed—Liquefactions of the same separately —His 
letter of December 2, 1877, to the French Academy—Ljiquefaction of nitro- 
gen—Of hydrogen—Rival claims of Cailletet and Pictet—Mercury stopper 
method—Manometers—Original methods of testing—Hiffel tower mano- 
meter—Carbon dioxide experiments—Mercury pump—High pressure gas 
reservoir—Ethylene as a refrigerant —Closed cycle method—Accelerated 
evaporation—Electric conductivity at low temperatures—Comparison of 
thermometric methods—La Tour’s experiment repeated. 


CHAPTER X.—SIGMUND VON WROBLEWSKI AND KARL 
OLSZEWSKI. - Pages 203-229 


Wroblewski’s life--Banishment from his native country—Early scientific 
work—His association with Olszewski—Study of Cailletet’s methods—Their 
apparatus—Defective position of the hydrogen thermometer—Liquefac- 
tions of oxygen, carbon monoxide and nitrogen—Ethylene data—Solidifi- 
cation of carbon disulphide and alcohol—Determination of the critical 
pressure and temperature of oxygen—Ljiquefaction of hydrogen—Use of a 
thermo-electric thermometer—Electric resistance of metals at low tempera- 
tures—Two liquids from air—Olszewski’s individual work—Apparatus for 
producing liquid oxygen in quantity—Comparison of platinum resistance 
and of hydrogen thermometers—Determination of hydrogen constants. 


CHAPTER XI.—JAMES DEWAR. Pages 231-285 


Dewar’s life and education—His associates—Controversies with Cxilletet as to 
priority—Karly liquefaction apparatus—Solid nitrous oxide as a refriger- 
ant—Royal Institution apparatus—Cooling cycles employed—Laboratory 
apparatus —Vacuum vessels—Air as a heat conveyer—Experiments with 
incandescent lamps—Reflection of ether waves from vacuum vessel—Keep- 
ing power of vacuum vessels—The Dewar vacuum—Its extraordinary per- 
fection—Analogy with population of earth—Experiment in slow diffusion 
of mercury vapor—Incidental production of vacuum vessels—Elasticity and 
strength of metals at low temperatures—Apparatus used—Hlongation of 
metals when stressed at low temperatures—Determination of specific and 
latent heats of liquefied gases—Gas-jet experiments—Low temperatures 
thus obtained—Freezing air—Large jet apparatus—Analysis by liquefaction 
—Ljiquefaction of fluorine—Liquefaction of hydrogen and helium—Experi- 
ments to show the intense cold of liquid hydrogen. 


CHAPTER XII.—CHARLES E. TRIPLER. Pages 287-296 


The life of Charles EK. Tripler—His early experiments with gas motors— 
Mechanical difficulties encountered—His electrical experiments —Chemistry 

*—His work in fine art—Exhibition of his paintings—Return to the investi- 
gation of compressed gases—Liquefaction of air—He endeavors to utilize 
the low grade heat of the universe—Simplicity of his apparatus—The plant 
—The compressor—General plan of operations—Capacity of his plant— 
How he transports liquid air--His lectures—Raoul Pictet in Charles E. 
Tripler’s laboratory. 


TABLE OF CONTENTS. 


CHAPTER XIII.—THE JOULE-THOMSON EFFECT. 
Pages 297 -306 


First attempts at liquefying gas—Joule and Thomson and their discovery— 
Coal a cheap chemical—Substitution of mechanical for chemical energy- 
Sir William Siemens’ regeneration of cold—Self-intensive refrigeration— 
Negative Joule-Thomson effect—Mathematics of the theory—Conditions of 
pressure for economical application. 


. 


CHAPTER XIV.—THE LINDE APPARATUS. 
Pages 307-319 


Linde’s apparatus—The simplest form of apparatus—Its operation—Its stor- 
ing of air at atmospheric pressure—Avoidance of atomization and waste— 
Subdivision of pressure-drop—Laboratory apparatus—A feature of ineffi- 
ciency in it—Its power of liquefaction—Continuous oxygen-producing appa- 
ratus—Date of Linde’s first successful use of his apparatus. 


CHAPTER XV.—THE HAMPSON APPARATUS. 
Pages 320-324 
Hampson’s apparatus—Its general features of construction—The jet and 
regulating device—Thermal and mechanical advantages—Data of its opera- 


tion—Use of cylinders of compressed gas instead of pumps—Application of 
preliminary cooling to the air or gas to be liquefied. 


CHAPTER XVI.—EXPERIMENTS WITH LIQUID AIR. 
Pages 325-337 


Experiments with liquid air—Formation of frost on bulbs—Filtering liquid 
air—Dewar’s bulbs—Liquid air in water—Tin made brittle as glass—India 
rubber made brittle Descending cloud of vapor—A tumbler made of frozen 
whisky—Alcohol icicle—Mercury frozen—Frozen mercury hammer— 
Liquid air as ammunition—Liquid air as basis of an explosive— Burning 
electric light carbon in liquid air—Burning steel pen in liquid air—Carbon 
dioxide solidified—Atmospheric air liquefied—Magnetism of oxygen. 


CHAPTER XVII.—SoOME OF THE APPLICATIONS OF LOW 
TEMPERATURES. Pages 338-356 


Frigotherapy—The frigorific well—Pictet’s experiment—Effects of the first 
trial of the system—Medieal-uses of liquid air—Critical point as test of pur- 
ity of chemicals—Purification of chemicals by low temperature crystalliza- 
tion—Low temperature distillation—Regulation of chemical reactions by 
cold—Liquid air explosives—The principle of their action—Liquid air in 
electric power transmission—Liquid air as a reservoir of energy. ad 


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LIQUID AIR 


ANDY PEs 


LIQUEFACTION OF’ GASES 


GHAPTER: Tf. 
PHYSICS. 


What is liquid air?—The three states of matter: Solid, 
liquid, and gaseous—Relations of pressure and heat to 
state assumed by matter—The critical state and its phe- 
nomena—Natterer’s tube—Physical units—Space, mass, 
and time—Force and energy—Conservation of force an 
abandoned doctrine—Conservation of energy—Work a 
synonym for development of energy—Waste of energy 
and entropy—Possibility of utilizing the lower forms of 
energy of the universe. 


A question has often been asked latterly; it is, 


*, ‘‘What is liquid air?” The subject has been so 


much discussed, and so much has been made of it, 
that it is hard to believe that there isnot some . 
occult mystery attending it. Liquid air is simply 
aix which is so cold that it assumes the liquid state. 
The fact that the question has been so often asked 
» suggests the need for a thorough answer; for back 
of it there lies a great region of physics and chemis- 
try, a summary exploration of which in the light of 


{0 LIQUID AIR AND THE 


the knowledge of to-day cannot but be interesting. 
In it are concerned the great doctrine of the con- 
servation of energy, the laws of heat, the three 
states of matter, and the chemistry of air, and it is 
not expecting too much of the reader of to-day to 
hope that the theory of the subject presented within 
the compass of an hour’s reading will interest him. 

The account of the liquefaction of gases includes 
a period of about one hundred years, and with it is 
bound up the history of the Royal Institution of 
London. In its laboratory Faraday worked with 
bent tubes, liquefying gases and blowing the tubes 
to pieccs and nearly blinding himself in his efforts. 
This was half a century ago and more. And now 
within its walls, with elaborate machinery based upon 
Pictet’s circuits of 1877, James Dewar, the successor 
of Faraday, liquefies hydrogen and helium and ends 
the century’s work. 

In Switzerland and France, toward the end of 
1877, the beginning of the cnd appeared when oxygen 
was liquefied. Pictet and Cailletet were the rivals, 
separated only a few days in their liquefaction of 
this gas, discovered by Priestly and Lavoisier almost 
exactly one hundred years betore the date of its re- 
duction to the liquid state. 

America was not idle. Tripler working away @ 
privately, with no institution or association to back 
him, has surpassed the dreams of the most enthusi- 
astic visionaries and has made liquid air by the barrel, 
and has sent it all over a wide range of country 4f 
tin cans. 

The long record should not be read until the® 
answer to the query cited above has been given; the * 


LIQUEFACTION OF GASES. II 


reader should know accurately what liquid air is, 
what constitutes a gas, what the relations of heat and 
pressure to state of matter are, and how heat is 
treated by the modern scientist. | 

Matter is generally stated to exist in three forms 
or states—the solid, liquid and gaseous. An attempt 
has been made to assert the existence of a fourth 
state—the ultra-gaseous or radiant state. There is a 
certain objection, however, to this. The first three 
states are broadly differentiated. As a rule, there is 
little question of the form or state being solid, liquid 
or gaseous, but the ultra-gaseous state is only recog- 
nizable by rather refined tests and may perhaps be 
better considered as the extreme carrying out of the 
gaseous condition. 

Water is the most convenient substance to cite to 
illustrate the three states. In ice we have solid 
water. The masses are of fixed contour, and, even if 
ice is subject to a species of flow, the masses of ice 
definitely hold their shape. The molecules of solid 
water are in constant vibration back and forth over 
the same path, under any conditions of temperature 
we are familiar with. At the absolute zero this 
motion would cease. The paths are inconceivably 
short. Wecannot and probably never will acquire any 
direct knowledge or sight of these vibrations. All 
we know is that ice at mundane temperatures is hot. 
It will be seen that, dropped into liquid air, it makes 
it boil as if the ice were a red hot poker thrust into 
it. By the kinetic theory of heat all hot bodies are 
held to have their molecules in constant vibration. 
Molecular attraction holds the particles of the ice 
firmly together in spite of this vibration. 


12 LIQUID AIR AND THE 


If we apply heat, we diminish this attraction, 
we increase the repulsive forces, and the ice reaches 
a temperature where the two opposing forces about 
balance each other, the attractive ones slightly pre- 
ponderating. Now there is no longer a powerful 
set of forces in operation binding the molecules 
together. They begin to slide about on each other, 
their vibrations continue with energy, but the paths 
vary. Amolecule bounces back and forth like a billiard 
ball, recoiling to right or left from its neighbor, so that 
sooner or later it travels through the entire mass and 
néver ceases its travels: } As the molecules slide 
about without true friction the ice loses all tendency 
to preserve its shape and falls to pieces, literally 
speaking. In other words, the ice melts, and we have 
water-—a representative of the liquid state of matter. 

Let us apply more heat. Our water is already 
shapeless. We have to keep it in a containing vessel. 
Evenadropof water hanging from the window shutter 
ona rainy day is held ina little sack of water-film. 
Later on we shall see what an important bearing the 
liquid film has inthe manipulation of liquid air. So 
we put our water in a kettle and heat it. Soon a 
white cloud issues from the spout, and we may say 
that we see the steam. If we make such an assertion, 
it 1s an erroneous One, as the white cloud is really 
composed of little balls of liquid water, each held in 
its own little sack of water-film. Asthe kettle boils 
harder, we find that the white cloud ‘does not begin 
its existence until it is a few inches from the mouth 
of the spout, and a space apparently void of all 
matter intervenes between spout and white cloud. 
This space is filled with the substance we are in 


LIQUEFACTION OF GASES. 13 


search of; it is occupied by a column of gaseous 
water or steam rushing out of the spout and as in- 
visible as air itself. 

By applying heat to our water, we have made the 
molecules vibrate through paths many times longer 
than the old paths; a cubic inch of water gives us 
approximately a cubic foot of steam. The molecules 
travel about through the mass with greater rapidity 
than ever. The mass loses all pretensions to shape 
or cohesion. A vessel will not hold it unless it is 
elosedsevcnywuere. dite third state” ot matter is 
formed—the water exists as a gas. 

By refinement of observation and experiment most 
interesting and captivating views are formed concern- 
ing these states of matter. Their individual prop- 
erties are not so sharply cut off and defined as might 
be supposed. <A body is said to be solid when it is 
practically unchanging in the shape imparted to it. 
But many solids flow under pressure. The suffering 
“continuous deformation under the action of a con- 
tinuous force” is not a certain criterion of .a liquid, 
but it is good enough to define it or identify it by. 

A barrel of asphalt opened and thrown on its side 
in the street seems to be filled with a black solid, yet 
by the end of the day it will have flowed -and 
changed shape. A stick of sealing wax supported 
at its ends slowly and continuously bends. Some 
authorities consider these as examples of liquids. 

A soft jelly pressed by a spoon yields consider- 
ably, but, when the pressure ceases, springs back into 
its original shape. Jelly, therefore, is treated as a 
solid. 

All this seems to cast confusion on. the subject. 


14 LIQUID AIRSAND: THe 


But nothing very critical hinges on the sharp sepa- 
ration of solid, liquid and gas. It would perhaps be 
better to assume a continuity of state between solids 
and liquids, and to consider asphalt, sealing wax and 
the like as being on the border line. If sealing wax 
is to be considered a liquid, then lead and most other 
metals could be considered such; for metals, asa rule, 
are more or less malleable and ductile, and the quali- 
ties of malleability and ductility depend upon the 
flow of the material composing them. 

We are confronted with the old property of nature 
expressed in the adage, Natura non facit saltum, 
Nature does not jump. The air we breathe is in the 
gaseous condition. The water we drink is in the 
liquid condition. The glass which holds the water 
is in the solid condition. Yet we can indicate many 
cases where an intermediate state exists and where a 
substance cannot well be termed one thing or the 
other. Even air is not a perfect gas, and hydrogen 
is an ultra-perfect gas. 

For want of correct understanding of such things 
as these, confusion in ideas results and an obscurity 
bordering upon complication is introduced into our 
conception of the laws and system of nature. Thus 
moist air is generally considered heavier than dry 
air, presumably because a wet cloth is heavier than 
a dry one. Popularly, people would say that the air 
is damp and heavy. Now air is wet because of the 
mixture with it of another gas, gaseous water or 
literally steam. Water from rain, from the ground 
and from the immense cvaporating surface of the 
leaves of the vegetable world assumes the gaseous 
form and mixes with the air. The specific gravity 


LIQUEFACTION OF GASES. 15 


of water in the gaseous condition is less than that of 
air. It is about two-thirds as heavy only. Wet air, 
therefore,is lighter than dry air. <A balloon would 
rise better on a dry day than on a wet day, not only 
because there would be no moisture with which to 
dampen the cordage and cloth, and thereby increase 
the weight, but because the dry air is a better float- 
ing medium than wet air, because it is heavier. 

Wet air is not air soaked like a sponge with water.| 
It is simply a mixture of dry air with gaseous water, 
The truth is here far simpler than fiction. 

The sequence followed by a substance in passe 
from state to state is not always the same, as a solid 
on heating is often vaporized or gasified directly 
without passing into the liquid state at all. This 
occurs in slow vaporization very often. Thus ice in 
the open air below the freezing temperature wastes 
away by volatilization and is gasified slowly, with- 
out liquefying, and contributes water vapor to the 
air, although far below the solidifying temperature. 
fodine volatilizes in the same way, and those who 
have used camphor or naphthaline for preserving 
clothes from moths have observed the same mysteri- 
ous diminishing of the lumps of preservative used. 
In druggists’ windows the shrinkage of camphor 
there exposed is sometimes quite striking. Now it 
is less often exposed than formerly, as naphthaline 
has largely supplanted it in the trade. 

Carbon dioxide, the gas which escapes from soda 
water and other effervescent beverages, when sub- 
jected to cold and pressure, liquefies. When the 
pressure is released and it is allowed to escape into 
the open air, it solidifies and produces a true carbon 


16 LIQUID AIR AND THE 


dioxide snow. This snow exhibits surprising per- 
manency, disappearing quite slowly in the open air- 
In disappearing it evaporates and produces gas 
directly without passing through the intermediate 
liquid state. 

Such direct transition from a solid into a gaseous 
state is termed often sublimation ; an expression, per- 
haps, too limiting, covers the extreme case where a 
solid on application of heat sublimes vigorously before 
melting. It is to the effect that the substance boils at 
a lower temperature than that at which it liquehes— 
that the temperature of boiling is lower than that of 
liquefaction. The idea of a solid boiling seems rather 
odd. 

It is not only the change of temperature which 
brings about change of state. Change of pressure 
allects it greatly. The greater the pressurcierae 
higher is the temperature at which a liquid becomes 
agas. A gas just hot enough to hold that form may, 
under some conditions, be converted into a liquid 
by applying pressure, without any change in tempera- 
ture being required to effect the change of state. 
This, too, is very natural. Foralquid, under ordin- 
ary conditions, being of smaller volume than the same 
molecules gasified, is naturally brought to the liquid 
condition by mechanical reduction of volume as well 
as by thermai reduction. 

Pressure will not always do it, and by combining 
the effects of great heat and great pressure, conditions 
foreign to the ordinary status of matter are brought 
into existence which complicate the problem. Heat 
is the great and all-controlling agent. Heat is what 
establishes the critical state, and pressure is quite a 


. LIQUEFACTION OF GASES. Leys 


secondary matter. [or every gas there is a critical 
temperature and a critical pressure, but the latter is 
quite a subsidiary thing, and is not critical in the full 
sense that the temperature is. 

Pressure tends to liquefy a solid, if the latter grows 
smaller on liquefaction. So that it is quite conceivable 
that a point might be reached where pressure would 
help to convert aliquid into a gas. As such a phe- 
nomenon, uncomplicated by other factors (page 24), 
has never been observed, it is better to set it aside 
and consider pressure as invariably on the side of 
cold in liquefying gases. 

A gas must be pictured to the imagination as a 
very active thing. In a room full of air the molecules 
are moving about rapidly, colliding with each other, 
and bounding about like billiard balls. We know 
that, if we turn on the gas without lighting it, in a 
very few minutes the odor of gas will be perceived 
in all parts of the room. This can only be so because 
in those few minutes the gas has penetrated every 
corner.. Its molecules have traveled about until 
some of them are everywhere present, and the 
activity of their operations may be judged by the 
amount of gas and the size of the room. An ordinary 
burner delivers one cubic foot of gas in about ten 
minutes, and in that time a room of over a thousand 
times that volume would be pervaded with it. Hence 
it will be seen how active the molecules of a gas 
are. | 

If there were no wind, if the air were absolutely 
motionless, its molecules would be as active as ever 
in their own spheres. The air which on one day 
would be in America would be scattered the next 


18 LIQUID AIR AND THE 


day far and wide, and its molecules would find their 
way sooner or later all over the world. 

The same is true in a lesser degree of liquids: 
The water of a tideless, currentless lake is in mole- 
cular motion. The water which beats against the 
coast of America is in constant process of change, 
and its molecules are changing and moving about all 
the time. Sooner or later some of them will be in 
the waves which break upon the Irish cliffs and 
English beaches, nearly three thousand miles away. 
They would travel thus were there no oceanic cur- 
rents and no waves. 

This molecular travel is termed diffusion. 

We have seen that the motions of the molecules 
_ are increased in vigor by heat, that, if heat is with- 
drawn, they decrease in intensity. The obvious 
question arises, What would happen if there were no 
heat? The molecular motions would cease, and 
molecular death would ensue. 

The passage of a substance from the solid to the 
liquid state or from the liquid to the gaseous state 
involves generally a change in dimension or size, and 
in the case of many substances the liquid state is the 
one of smallest size. Thisis the case with water. In 
round numbers, a pint of water gives nearly a pint 
and two ounces of ice, if it freezes, and if converted 
into steam, gives nearly two hundred gallons. We 
are most concerned with the liquid and gaseous 
states, and under ordinary circumstances there is a 
very great reduction of volume incident to the pass- 
age of a substance from the gaseous to the liquid 
State. 

It follows that, to produce liquefaction of a gas, 


LIQUEFACTION OF GASES. 19 


the first thing we should naturally try to do would 
be to reduce it in volume, and the simplest way to 
do this would be by pressure. Early experimenters 
adopted this plan. Natterer attained pressures of 
many thousand pounds to the square inch, yet gases 
compressed to a small fraction of their volume staid 
gases and refused to yield. 

At last Andrews, of Belfast, made his classic dis- 
coveries, and the existence of a critical state was es- 
tablished. This stateis very easy to understand. It 
depends on the fact that for every gas there is a 
temperature called its critical temperature, and a 
corresponding pressure called the critical pressure. 
When hotter than this temperature, no compression, 
however great, will liquefy it. Below this tempera- 
ture, a compression easy of attainment is enough to 
effect the change to the liquid state. 

The critical pressure is a term which is often mis- 
understood. It may be said that the pressure is 
never Critical in the full sense in which temperature 
becomes critical. There is no pressure which can be 
defined as so low that liquefaction would be impossi- 
ble init. There is a theoretical point of cold never 
yet attained, which is termed the absolute zero. At 
this point heat ceases, the molecules no longer 
vibrate, and absolute cold exists. If a body were 
reduced to the absolute zero, where the motions of 
the molecules cease, pressure would be without 
effect upon it, as its only power is to shorten the 
paths of vibration of the molecules. The term criti- 
cal pressure is used to describe the pressure required 
to liquefy a gas when it is at the critical temperature. 

When a gas is at the critical temperature and at 


20 LIQUID AIR AND THE 


the critical pressure also, the least increase of 
pressure or decrease of temperature will convert it 
into a liquid. When in this condition, ready to bea 
gas or a liquid, it is said to be in the critical state. 

It will be seen how very well the term critical 
state applies when a substance is at the critical 
pressure and temperature, the least change will so 
profoundly modify its state. 

A law relating to the critical state is known as 
La Tour’s law, and expresses very succinctly the 
phenomenon of the critical temperature. It is the 
following : | 

There is for every vaporizable liquid a certain 
temperature and pressure at which it may be con- 
verted into the aeriform state in the same space occu- 
pied by the liquid. 

It will be evident how strikingly this puts the fact. 
that, above a certain temperature, a gas can be 
squeezed down to the volume of its mass as a liquid 
without liquefying. If a gas rigorously followed 
Mariotte’s law and changed in volume in inverse 
proportion to the pressure exerted upon it, and if 
pressure sufficient to reduce it to the absolute 
volume, as it may be termed, or the volume it should 
have at the absolute zero, were exerted upon it, it is 
hard to say what would become of it. 

The condition of a substance in the neighborhood 
of the critical state is sometimes termed the inter- 
mediate state. The expressions are almost synony- 
mous—the first is the more abstract, the latter the 
more concrete expression. 

The reduction from the gaseous to the liquid state 
is usually a reduction of volume. <A cubic foot of 


LIQUEFACTION OF GASES. BY 


steam gives about a cubic inch of water; eight hun- 
dred cubic inches of ordinary air give about a cubic 
inch of liquid air. But owing to the phenomenon of 
the critical temperature, or, what is the same thing, to 
La Tour’s law, this is not always true. The existence 
of a gas of no greater volume than the liquid it could 
be converted into is asort of scientific riddle. It 
has its counterpart in the inexplicably great power 
of expansion by heat possessed by some liquefied 
gases without departure from the liquid state. 

The passage of a substance from the liquid to the 
gaseous state is marked by a change of appearance 
A liquid has always a defined limit. It lies in the 
containing vessel and its upper surface forms a visi- 
ble boundary. If the vessel is of large diameter, the 
surface is level and flat, except along the edges, 
where it curves up ordown alittle. If the diameter 
is small, it curves throughout its whole extent, form- 
ing a little cup or a little hill, as the case may be. 

The upper curved surface of a liquid is termed the 
meniscus. Mercury in a glass tube forms a convex 
meniscus; water, a concave one. For different 
liquids in contact with solids the meniscus varies, a 
characteristic one obtaining for each condition. 

A very interesting suggestion is due to Jamin. 
It is that when oxygen and carbon dioxide are com- 
pressed together,a point may be reached when the 
carbon dioxide will liquefy but will be lighter than 
the compressed gas, so that we should have the 
curious phenomenon of a fluid floating upon a gas. 
Prof. Ramsay seems to think that he has observed 
this phenomenon. The meniscus in this case lies 
at the bottom of the liquid and above the gas. 


22 ae LIQUID AIR AND THE 


For years the disappearance of the meniscus was 
regarded as marking the change or transition from 
the liquid to the gaseous state. This view seemed 
satisfactory. But science is not restful. Doubts 
began to be cast upon the coincidence of this disap- 
pearance with the true transition. 

Thus in 1892 Zambiasi attacked the problem by 
experimenting with ether in a sealed tube and repro- 
duced the intermediate and critical state phenomena 
therewith. Cagniard de la Tour’s and Cailletet’s 
observations were studied with the more manageable 
ether. Zambiasi came to the conclusion that the 
appearance and disappearance of the meniscus, while 
occurring at a constant temperature for a given tube, 
occurs at different temperatures in different tubes, 
the temperature being determined by the relative 
proportion of liquid to gas in the tubes. 

In 1893 there were published a number of papers 
by Ramsay, Galitzine and others on the subject of 
the critical state and the uncertainty of the optical 
method, by simple inspection, of determining the 
transition from liquid to gaseous state. Quite an 
acrimonious discussion is contained in successive 
communications between the opposition scientists. 
The subject is left rather unsettled; the disappear- 
ance of the meniscus with some has lost its old time 
definite status, and the case is left pretty nearly in 
Statu quo. 

But the disappearance of the meniscus is not the 
only phenomenon of change of state. A peculiar 
flickering appearance is noted as indicative of it, to- 
gether with the formation of striaz, and so character- 
istic is this feature that it is used by Pictet in some 


LIQUEFACTION OF GASES. 23, 


of his most recent work as an indicator of gasefac- 
tion. 

If a tube is partly filled with a liquid, is sealed and 
heated, fhe first indication of a change of state to be 
looked for is the disappearance of the meniscus. As 
it vanishes, the flickering striz appear and a sort of 
unrest pervades the tube, and quickly the critical 
state is passed and the liquid has become a 
gas. 

The phenomenon is conveniently shown || | 
in a sealed tube half filled with ether, as || |//|jll 
shown in the cut. It is mounted within a | | 
larger tube filled with paraffin wax. The 
latter is opaque and solid when cold, but === 
on heating melts and becomes transpa- 
rent. On heating the wax, the liquid in 
the inner tube goes through the critical | | 
state, the phases can be watched, and the | 
phenomena described above can be seen. |i. 
If it is to be shown to an audience, the ii 
image of the tube is projected upona 
screen by the magic lantern, and the phe- | 
nomena are produced so as to be visible ||) 
by a roomful of spectators. The sealed ee ) 
tube is termed Natterer’s tube. ot 

Hannay and Hogarth, in 1880, in experi. N@tterer's 
ments on the critical state of matter, found oat 
that several salts, such as potassium iodide and bro- 
mide, would dissolve or volatilize in gaseous alcohol | 
fepoetenipetatureO1.375,4.0. (707, H:), the. whole 
being contained in a strong sealed tube. 

P. Villard (1898) extended the scope of this in- 
vestigation and got very interesting results with 


NUNN 


Nl 
ATI 

{| 
i 
1 


24 LIQUID, ATRZAND AA EE 


solids and liquids. As a liquid, bromine may be 
cited. This was placed ina tube with oxygen gas, 
and the pressure was gradually increased. Normally 
increase of pressure would be supposed to tend to 
keep the bromine liquid. But, on the contrary, at 
two hundred atmospheres, the bromine began to 
take the gaseous form and to dissolve in the com- 
pressed oxygen. The action of the dark brown 
liquid was exactly that of a substance entering into 
solution. The gaseous mixture took a darker color 
at three hundred atmospheres than that of a solution 
of bromine in water. Villard recalls Cailletet’s ob- 
servation that liquid carbon dioxide dissolves in 
air. We may also call to mind the “guzde Pictet 
(page17o) in this connection. 

Bromine is a brown liquid, and is one of the ele 
ments; its near neighbor, iodine, is a solid. The 
latter was found to dissolve in small proportions in 
oxygen. Formene was another gas which was ex- 
perimented with. It dissolved ethyl chloride, car- 
bon disulphide, alcohol, camphor, paraffin and 
iodine. In some cases the gas-solution phenomena 
were almost reproductions of the critical state phe- 
nomena, including the obliteration of the meniscus. 

A very interesting suggestion was made by Vil- 
lard; it was that gaseous solution might take the 
place of distillation as a laboratory operation. 

As the doctrine of the conservation of energy is 
intimately involved in the liquefaction of air and of 
all gases, something may be said of the relations of 
force and energy. This may more appropriately be 
done as it will bring forward a treatment of the sub- 
ject which may commend itself to some interested 


LIQUEFACTION OF GASES. 25 


in physics. This treatment of the subject is based 
on the substitution of two units for three. Usually, 
force, work and energy are the interrelated units ap- 
pealed to in treatises on mechanics. The far more 
desirable way is to follow out the theory of dimen- 
sions and to take two of these units only as the 
foundation stones of the science. These two are 
force and energy. Work, instead of being awarded 
an important place, should be treated only as an 
adjunct and convenient expression of the concrete 
and accidental. This sounds, perhaps, heterodox. 
It is really orthodox, and is a move in the direction 
of avoiding confusion. . 

As music is built up out of a few notes, as the 
twenty-odd letters of modern alphabets in a sense 
are the basic units of the written languages, so we 
have certain fundamental elements in natural science. 
These may, for our purposes, be stated as distance or 
linear space, mass and time. These are familiar to 
all. The accepted units are the centimeter (0°39 
inch), gramme (15°43 grains) and the second. Then 
there are two derived units, less familiar in their 
scientific status, and less generally understood, 
than the others cited above. These are force and 
energy. 

Distance is linear space, space measured along a 
line, space of one dimension. A foot, an inch, a 
centimeter, are units of distance. An attempt was 
made to get an absolute unit by taking one ten- 
millionth part of the quadrant of the earth as a unit. 
This is what the French meter was supposed to be, 
but the measurement was inexact; so the unit is as 
truly inexact as was the old time barleycorn, except 


20 LIQUID AIR AND THE 


in degree. Its exactness was many times greater, as 
it approximated at least to a fixed standard, and the 
length of a barleycorn is as unfixed a standard as 
could well be imagined, although our system of 
measures is based on it. Three barleycorns make 
one inch, and the exceedingly exact standard yard 
measures carefully preserved by the British and_ 
American governments had their origin in the 
length of a corn of barley. The most recent and 
scientific unit of length is the wave length of a given 
monochromatic light. But for everyday purposes 
the foot is very generally used in this country. 

Time is the measure of duration and is the function 
having a truly international unit, the second. This 
is an astronomical unit, and’ might be used as a basis 
of all others. The proposal to do so has been made, 
but has never been carried out. 

Mass indicates the quantity of matter ina body. 
It is a somewhat unfortunate unit, as it is constantly 
confused with weight. A piece of iron hasa definite 
mass, but it weighs one amount at the equator and 
another amount at the poles. On the surface of the 
moon it would weigh far less than on the surface of 
the earth. From one point of view the proper unit 
ot mass would be equal to a pound, or a gramme, or 
whatever may be taken as the unit of weight divided 
by the velocity a body acquires in falling through a 
vacuum forone second. As this last quantity varies 
at different parts of the earth, it would seem that 
the unit of mass should in some way be fixed, and 
that the unit of weight should vary. Accordingly, 
the quantity of matter in one gramme is taken as the 
unit of mass. Weight varies, for a pound of sugar 


LIQUEFACTION OF GASES. 27 


at the poles is slightly greater in mass than a pound 
at the equator. This is very scientific, but does not 
square with the relative sweetening power of the two 
pounds. 

We have just spoken incidentally of velocity. 
This is a unit which indicates the distance passed 
over in a second. As two unitary quantities, time 
and distance, are involved, it is compound. 

We are now ready to see what force and energy 
are. They are the hardest of all to grasp. Had 


Faraday and a host of others grasped their signifi. — 


cance, the erroneous doctrine of the conservation of 
“force’’ would never have been invented. 

Force may be variously defined. Newton’s defini- 
tion of it as given by Daniell is ‘“‘a measurable action 
upon a body, under which the state of rest of that 
body, or its state of uniform motion in a straight 
line, suffers change.” But force may be exerted 
without producing any such change, so that the de- 
finition, like many others, is not satisfactory. A copy- 
ing press applies force to the book it squeezes as 
long as the screw is left turned down, but it imparts 
no change of state of motion or of rest to the book. A 
spring held by a catch of any kind so as to be in a 
state of tension exerts force against the restraining 
piece, but there is no question of change of state of 
motion or of rest. The definition of force as that 
which exerts a pressure or a pulling stress upon 
anything, or between any two or more masses, is, 
for ordinary purposes, an exact enough definition, 
though not a very elegant one. 

The total forces exerted in the universe may vary 
constantly in amount. There is no such thing as the 


28 LIQUID AIR AND THE 


conservation of force, conservation meaning, in such 
a connection, constancy or invariability of quantity. 
Force may be called into existence and annihilated at 
will. It varies ad “bitum just as motion does. A 
man may run or wa.-k or stand still. He thereby 
creates or annihilates motion. Hemay do the same 
for the force he exerts by his own control. 

Not many years ago a work was published on the 
subject of the Conservation of Force. It was made 
up of extracts from the writings of various scientists 
which treated of the supposedly true doctrine of 
the conservation of force. Among other writers — 
Faraday was quoted, and it is curious to see how he 
could not reconcile the contradictions of the sup- 
posed law. He accepted it on the weight of 
authority of others, his acceptance giving a lessonin 
humility which some doctrinaires of the present 
day might profitably study. 

All the while the doctrine was an utter falsity and 
is now discarded absolutely. It is one of the monu- 
mental errors of the scientific world. It shows that 
students of science have their own errors to contend 
with and guard against. We can reasonably believe, 
however, that we are not fast bound at present in any 
such error, at least in the field of physics. 

Faraday, who has been cited above, was one of the 
loveliest figures in modern science and his appearance 
here is not the only one he makes in the pages of 
this book, as he appears as one who paved the way 
for the liquefaction of air and for that of the so- 
called permanent gases. He itis who gave one of 
the first blows to this name. 

There is one survival of the erroneous doctrine 


LIQUEFACTION OF GASES. 29 


which, although it only affects the nomenclature, is 
interesting to notice. It is the term “living force,” 
which cannot be said to have quite disappeared from 
the language. It was long used as the expression 
for mechanical energy. The French, who are more 
conservative than we, adhere to it far more tena- 
ciously, and its equivalent is found in many recent 
scientific papers in that language. The term is a 
metaphorical presentation of the idea of force in 
action, and force in action is nothing more or less 
than energy. If the action is positive, it is the 
exertion of energy ; if the action is negative, it is the 
development and consequent absorption of energy. 

But the best method of avoiding confusion in 
modern science is to concentrate the nomenclature 
and to avoid useless multiplication of terms. So the 
term living force, picturesque as it is, is very pro- 
perly abandoned for the more concise term energy. 

Energy is a unit which expresses the action of a 
force along a distance. If a man pushes against a 
car, and all remains stationary, he exerts, properly 
speaking, no mechanical energy, but only force. But 
if the car moves, and he follows, pushing it before 
him, his force is exerted along a distance, and the 
compound force-distance unit thus indicated is called 
energy. Two actions are involved. The man ex- 
pends energy and gets rid of it. It disappears. But 
the car receives energy, and in the overcoming of its 
inertial and frictional resistances an amount of energy 
is received by it precisely equal to that which has 
disappeared. This energy is largely converted into 
heat. . 

Suppose an athlete holds a dumbbell by his side 


30 LIQUID AIR AND THE 


and raises it to arm’s length. The dumbbell weigh- 
ing ten pounds and the lift being four feet, he would 
have expended on it energy represented by the pro- 
duct of force and distance. The force may be 
popularly expressed in this case as ten pounds, the dis. 
tance is four feet ; the energy expended is forty foot- 
pounds. The energy which he spent in lifting the 
dumbbell has disappeared, and in its place has been 
created the energy now inherent in the lifted mass. 
By virtue of its position the dumbbell has an ability 
in recovering its old position to exert energy in its 
own turn. if the bell drops the four feet, it will, in 
doing so, lose its favorable position and exert energy. 
The exerted energy will disappear and cease to exist, 
but in its place a precisely similar and equal quantity 
of energy will be developed. 

Suppose now that the dumbbell is allowed to fall 
the four feet through a vacuum. At the end of its 
fall it will be moving quite rapidly and will be able 
to strike quite a severe blow. This blow it can in- 
flict by virtue of the energy inherent in it. As this 
is derived from a fall of four feet, it will be measured 
by distance and force as before, by forty foot-pounds. 
If it strikes its blow and comes to rest four feet from 
its starting point, its energy will disappear, and in 
some form or other forty foot-pounds of new energy 
will be created. 

The reader will observe that the dumbbell held 
motionless four feet above its level of rest has the 
- power, when called upon, of exerting in its descent 
the forty foot-pounds of energy which the athlete 
exerted on it. It possesses the power of exerting 
energy, which power is termed potential energy. 


LIQUEFACTION OF GASES. 31 


Reaching the end of its four-foot fall, it then is 
charged with energy real and positive, by virtue of 
which it can inflict a blow. This is the energy of 
motion or kinetic energy. 

Illustrations could be produced in any desired 
quantity. It would be found that whenever energy 
disappeared, an equal quantity of other energy 
appeared. - This law holds good always without any 
exception, and is universally accepted as fixed and 
invariable. It is most generally expressed by say- 
ing that the total energy of the universe is always 
the same in amount. 

It will be noticed that the term “work” has not 
been used in this brief exposition. Usually, it is one 
of the first things cited in such cases, and energy is 
defined as the power of doing work. But it is 
much better to keep the fact clearly before us that 
energy is the important and more fundamental unit, 
and that work is simply another term for develop- 
mento sencroy.s). lo, “do swork,y..is. 10, expend 
energy. Our athlete, in raising the dumbbell, ex- 
pends his own energy, develops new energy, and the 
latter is the doing of work. The particular energy 
exerted by the athlete ceases to exist, and is re- 
placed by an exactly equal amount of energy devel- 
oped in the dumbbell by its change of position. The 
dumbbell, it would generally be said, has had work 
done upon it, the lifting of it constituting work; it 
is far more logical to term this hfting the develop- 
ment of energy in the object acted on. 

It would seem somewhat presumptuous to at- 
tempt.to do away with the term work, and the word 
is so convenient, and is in such universal use among 


32 LIQUID AIR AND THE 


physicists, that it cannot be dropped. It should, 
however, be treated rather as a convenience than as 
a real physical unit, and it should always be under- 
stood to be a shorthand term and synonym for-de- 
velopment of energy. If work is performed, it is 
development of energy that is performed, and the 
object which does the work expends energy in de- 
veloping new energy. ; 

There is a very simple experiment, which anyone 
can try, which supplies an excellent illustration of 
the conversions of energy. An india rubber band is 
held by the two hands across the mouth, so as just 
to lie between the lips.. -It 1s now’ stretched: 
The ‘energy’ of the® éxperimenter: is ~ spentesonm 
stretching the band; some other equivalent of 
energy must be developed to take its place. As 
‘the band stretches, the lips can feel it grow 
warmer. The mechanical ‘energy expended in 
stretching it is converted into the kinetic energy of 
heat. It is allowed to resume its original length. 
In doing so, it exerts energy. It has only the kinetic 
energy of its heat to call upon. ‘Accordingly, it 
grows cool as it resumes its original length, and the 
lips feel the cooling effect. It illustrates the law of 
the conservation of energy excellently, and is parti- 
cularly interesting to the reader, as it applies very 
strikingly to the expansion and contraction of gases. 

We can now appreciate the conception of a reser- 
voir of energy. The pound weight, held at four feet 
elevation, exerts no energy, but does exert force. It 
is a reservoir of energy in potential form. The 
same weight, moving with the velocity acquired by 
a fall of four feet, is a reservoir of energy in 


LIQUEFACTION OF GASES. 33 


yee 10mn.. rout: toysrest alter ats<fall; the 
kinetic energy it was charged with disappears and 
it is no longer a source or reservoir of energy. 

When energy is expended by any mechanism, the 
new energy developed to replace the old in the 
world’s scheme, and to keep the amount of the 
world’s energy invariable, is apt to take largely the 
form of heat energy. A railroad train has expended 
on it the energy of the locomotive. Suppose it runsa 
mile upon a dead level. At the end of the mile it 
occupies a position not one whit more advantageous 
than when it started, as far as energy of position is 
concerned. Yet the fire in the fire-box of the engine 
has fiercely burned over the mile run, and the en- 
ergy of the sun of bygone ages, stored up for geo- 
logic epochs in the inert coal, has been expended, 
What energy has been developed to take its place 
and keep up the balance? 

It is energy of heat. The wheels have pounded 
over the rails, heating themselves and the rails, their 
journals and the journal-boxes have been heated, and 
even the energy expended on overcoming the air 
resistance has heated it a little, and the sides of the 
cars have been heated a little also. This heat is 
absolutely useless, or even pernicious. We cannot 
move a train along a level roadbed, we cannot drive 
a ship across the level plain of the ocean, without 
expending energy which we can never recover. It 
goes into the storehouse of nature, never to be re- 
covered by man until another great step in advance 
is made. The liquefaction of air has in it a germ, 
dimly recognizable, which may enable us to utilize 
the low forms of energy with which nature is 


34 LIQUID AIR AND THE 


charged. The ocean path, and the steamer which 
traverses it, at the end of the Atlantic trip may have 
received one hundred and forty thousand horse power 
days of energy. Now it is all lost to man. Man’s 
ingenuity perpetrates no more wasteful and unsatis- 
factory acts than the transfer of himself and _ his 
possessions across the ocean or -over continents. 
The thirty thousand horse power engines of the 
transatlantic liner are no more a triumph of human 
ingenuity than in their enormous wastefulness of 
practically one hundred per cent. they are a conces- 
sion to his inability to utilize the energy of the 
universe. 

This brings us face to face with the doctrine of 
entropy. We have seen that the low degrees of - 
heating produced by the friction of machinery, and 
which represent its wasteful resistance, are lost for- 
ever to us. The potential chemical energy repre- 
sented by the separation of carbon and oxygen is the 
energy of carbon or coal which can be burned under 
a boiler when it unites with the oxygen of the air. 
This is one of the world’s energies which can be util- 
izcd by man, and these energies are called available 
energy orentropy. The world’s coal is being burned 
up, its forests are being destroyed, machinery is add_ 
ing to the irreclaimable energy of the world, and, by 
the doctrine of the conservation of energy, is destroy- 
ing that same quantity of available energy; hence 
the entropy of the universe is becoming smaller day 
by day. | 

Clerk Maxwell saw the possibilities of the utiliza- 
tion of the unavailable energies of the universe. It 

is provoking to know that our great ocean of air 


LIQUEFACTION OF GASES. 35 


is pulsating with molecular energy which we do not 
utilize. Yet we do utilize it ina sense in compressed 
air motors, we call upon it in liquid air work, and 
Clerk Maxwell’s dream of the utilization of the lost 
energies of the universe may yet come true by the 
application of liquid air and liquefied gases to motors. 
A pepular paradox, which has been much dis- 
cussed, may be used to give an example of the doing 
of work at the expense of the low grade heat of the 
air and of other matter. A steel spring is placed in 
tension or is wound up. It is then dissolved in acid. 
The question is, What becomes of the energy which 
seems to be present in the spring, and ready for 
utilization ? One theory is that there is present in it 
no energy which in any way is due to its being 
wound up. When first wound; the energy expended 
in the operation develops new low-grade heat energy, 
and the spring is shghtly heated. Then it loses the 
heat ina few seconds, and there is no,longer any 
more energy in it wound than unwound.; Therefore, 
it dissolves in acid without having any special 

, energy to account for, $ 
Now, the question may be asked, How can the 
spring, if it has no energy, drive a clock? It does 
this, not at the cost of any mechanical energy due to 
its tension, but utilizes the low-grade heat energy 
of which we have been speaking. As it drives the 
clock it gets cool, and the energy required to drive 
the clock is represented by this cooling. As air 
circulates around it, it recovers immediately any 
loss of temperature, so that no loss of heat is practi- 
cally discernible. But the clock is driven primarily 
by the heat of tne air, by heat such as is usually 


26 LIQUID AIR AND THE 


treated as unavailable. The india rubber band ex- 
periment described on page 32 is an exact illustra- 
tion of the point involved. 

Elsewhere che possibility of using liquid air as a 
substance for the storage of power is alluded to. If 
this were done, an engine could be driven by it exactly 
as by steam, except that the heat would be drawn 
from the atmosphere instead of from a burning fur- 
nace of coal, and there would be a utilization of low 
heat energy. 


LIQUEFACTION OF GASES, a7 


CHAPTER II. 
FEAT. 


Heat and its measurement—Thermometers—The zero point— 
The Celsius or Centigrade thermometer scale—Fahren- 
heit’s thermometer scale—The absolute zero—Its basis— 
Coefficient of expansion of gases—Determination of 
temperatures in the liquefaction of gases—Different 
liquids used in filling thermometers—The air thermome- 
ter—The hydrogen thermometer—Details of its con- 
struction—Electrolytic hydrogen—The hydrogen or air 
thermometer formula—The thermo-electric thermometer 
—Onnes’ i1lstrument and details of its construction—Its 
calibration—The electric resistance thermometer—Calori- 
metric determination of temperatures. 


Heat has been referred to. While all have a gen- 
eral idea of heat, the basis of the different thermome- 
ter scales may be spoken of, and the absolute zero 
defined more fully. 

Various thermometer scales have been proposed, 
andeetiree mares in, -eeneral@ use, - Ehermometers 
generally indicate the temperature by the move- 
ments of an indicator over a graduated scale. 
Mercury and colored alcohol are the substances 
whose expansion by heat is utilized for ordinary 
thermometers, and the upper surface of the column 
of mercury or alcohol forms the indicator. The 
scales had to be divided on some system or other. 
The first thing to be settled was where to place the 
zero point at which to begin the division. Fahren- 


38 LIQUID AIR AND THE 


heit placed it well below the freezing point of 
water. Reaumur and Celsius placed it at the point 
where ice melts, which is the freezing point of water 
also. A name forthis point is required, and the 
name zero, of Italian origin, from the same Arabic 
root as our word cipher, is given to it. Zero seems 
to apply more to thermometric scales than to others, 
simply because we are more familiar with this class 
of scales than with hydrometers and other scale- 
bearing instruments. 

At the zeros of the above thermometric scales 
an active molecular “motion exists; there is a 
quantity of heat present in all things, at and far 
below the zeros; ice is hot, ice water is hot, frozen 
mercury is hot. This seems illogical; nothingness 
on the thermometer scale should indicate nothingness 
of heat. As thermometer scales are graduated now, 
their zero points are placed in a locus of very con- 
siderable heat. They can only be called points of 
relative cold; we think them cold because of our 
physiological peculiarities. Bacteria do not seem 
to think that ice is cold; at least they live through 
freezing unimpaired in vitality. 

Two easily produced temperatures are used for 
establishing thermometer scales. Onc is the boiling 
point of water, the other the melting point of ice. 
By comparatively simple apparatus these tempera- 
tures can be reproduced at will, without need of the 
application of any difficult correction. For the gra- 
duation of ordinary thermometers no correction is 
applied, although the barometer reading should be 
taken into consideration. | 

The standard scientific thermometer is the Celsius 


LIQUEFACTION OF GASES. 39 


or Centigrade instrument. Inthisthe temperature of 
melting ice is taken as zero, that of boiling water, or, 
more accurately, of steam at atmospheric pressure, 
as one hundred, and the space between and above 
and below these points is uniformly divided off on 
that basis. 

One account says that Fahrenheit attempted to get 
absolute cold, that he made a freezing mixture with 
ice water and salt, or sal ammoniac, and took its 
temperature as being perfect cold. Then he took 
the temperature of the human body as another 
datum point, and tried to have the freezing point of 
water one-third way between his zero and the human 
body temperature. Of the three devisers of ther- 
mometric scales, he was the only one who made an 
attempt to get a genuine zero. In the early days of 
the eighteenth century, when Fahrenheit was doing 
his work, the kinetic theory of heat, which is what 
we are here describing, had not been evolved. It 
was in 1724 that his low temperature experiment was 
published. 

Another explanation of Fahrenheit’s thermometer 
is that he took as his zero a temperature observed 
at Dantzig, Prussia, which he found that he could 
always reproduce by salt and ice. He computed 
that at that temperature, which he believed to be the 
absolute zero, ashe interpreted it, his thermometer 
contained 11,124 parts of mercury, which expanded 
to 11,156 parts in melting snow. This gave him 32 
parts expansion, or 32 degrees. In boiling water he 
found his mercury had increased to 11,336 parts. This 
gave him (11,336—11,124=212) 212 parts or 212 de- 
grees between his zero and the boiling point. 


40 LIQUID AIR AND THE 


Absolute cold has been defined. It is the temper- 
ature at which all heat energy ceases—when the 
molecules would cease to vibrate, when molecular 
death would occur. This point is the starting point 
of the theoretically correct themometer scale—its 
zero. Were it not too late, the thermometer scales of 
the world should be based on this point as a starting 
point. 

This point is termed the absolute zero. It lies at 
273° C. below the Centigrade zero (—459°4° F.) 

A good temperature for a living room is 20° C, 
(68° F.) It would on the absolute thermometer be 
273+20=293° C. (527°4° F.) Instead of complaining 
that the mercury has gone up to 99° in the shade, 
we might correctly call it 558° in the shade and feel 
that we had better ground for complaint. The 
absolute zero has had a definite place assigned it, 
based on the properties of the form of matter which 
is acted on by heat with perfect freedom. It is the 
form of matter in which the molecules are free to 
move under the influence of heat unhampered by 
any individual attraction, in other words, the gaseous 
form of matter. 

Imagine a quantity of gas which we will suppose 
to have, at the freezing point, a volume of 273 cubic 
inches. If we heat it 1 degree Centigrade, it will 
become 274 cubic inches. Another degree rise of 
temperature will make it 275 cubic inches, and so on. 
If we cool it 1 degree Centigrade below the freez- 
ing point, it will become 272 cubic inches, and so on 
all the way down. The paths of vibration of the 
molecules thus grow smaller and smaller with each 
reduction in temperature, until we are led to the con- 


LIQUEFACTION OF GASES. AI 


clusion that, when the temperature has been lowered 
273 degrees, the gas, losing 1 cubic inch at each 
degree reduction, will have lost its entire volume, 
or will have been reduced as near to a volume of 
nothingness. as it can get. Now, the idea of its 
having a volume of nothingness or of a gas losing 
its entire volume being absurd, we substitute the 
theory that, at 273. degrees below freezing, the 
paths of vibration of the molecules will become 
infinitely short, that their length will become 
nothing, and that the molecules will rest. 

The absolute zero is based on these considerations. 
The proposition is stated and proved above ina very 
crude way, but it gives a simpler presentation of tne 
subject than is given in the ordinary statement of the 
subject. The law of the expansion of gases by heat 
may be thus more scientifically stated. 

If we start with a volume of gas at any tempera- 
ture and apply heat, it will increase in volume. For 
equal increments of heat it will increase identical 
amounts, or for equal increments it will increase 
equal portions of the original volume. Confining 
ourselves now to the Centigrade scale, we find that 
for increments of temperature of 1 degree, the 
-volume of a gas will increase by z4 3 of what its 
volume would be at the temperature of melting ice 
or zero Centigrade. This is termed the coefficient 
of expansion of gases. The same occurs for re- 
ductions of temperature. Therefore, at 273° below 
zero no more reduction in volume will be possible. 
At this point the motions of the molecules must Stop 
—it is absolute zero. 

The determination of the low temperatures em- 


; 42 LIQUID AIR AND THE 


ployed in experiments on the liquefaction of gases is 
naturally attended with difficulty. The mercurial 
thermometer had to be discarded because the metal 
solidified at a comparatively high temperature when 
referred to the degrce of cold attained in the experi- 
ments. Even in Faraday’s experiments the mercurial 
thermometer was discarded in favor of the aicohol 
thermometer. The degrees on the instrument he 
employed, which was a Fahrenheit thermometer, were 
graduated below 32° F. into degrees respectively 
equal in length to those between 32° F, and 212° F. 
on its scale. He got down to —110° C. (—166° F.) 
Not reaching the critical temperature of oxygen, he 
naturally failed in liquefying it. What Wroblewski 
and Olszewski term “a dazzling demonstration”’ 
(eine glanzende Bestatigung) is given by an experi- 
ment of Natterer, who shows that the incredible 
pressure of 3,00) atmospheres alone is insufficient 
to liquefy oxygen. When it is realized that the 
pressure in a modern cannon at its maximum is 
about two-thirds of this amount, it can be seen what 
the scope of Natterer’s experiment was. 

Natterer used a thermometer filled with phos- 
phorous chloride, as he orally informed Wroblewski 
or Olszewski (Wiedemann’s Annalen, 1883), and 
Cailletet, in his work on low temperatures, used a 
carbon bisulphide thermometer. Wroblewski and 
Olszewski used a hydrogen thermometer constructed 
on the model of Joly’s air thermometer (Poggendorff's 
Annalen, 1874). 

Wroblewski and Olszewski found a slight discrep- 
ancy between the readings of a carbon bisulphide 
and a hydrogen thermometer. The carbon bisulphide 


LIQUEFACTION OF GASES. 43 


instrument read about 2 degrees Centigrade lower 
than did the hydrogen thermometer. This reading 
was but a few degrees above the solidification point 
of carbon bisulphide, and under such conditions, 
namely, an approach to its solidification temperature, 
an irregularity in expansion and contraction is always 
to be looked for in a liquid. The carbon bisulphide 
thermometer scale is graduated on the basis of 
higher temperatures—the coefficient of expansion 
is much greater near the solidification point than it 
is higher up the scale. 

The same observers note that when the carbon 
bisulphide freezes in the thermometer, the tube breaks 
into several pieces. They found that a couple of 
minutes’ evaporation of ethylene in a vacuum was suf- 
ficient to freeze bisulphide of carbon. They put its 
freezing point at about —116° C.(—177° F.) It melts, 
they state, at about —110° C. (—166 F.) Common 95 
per cent. alcohol thickened at —129° C. (—200:2° F.) 
and froze solid at about —130°5° C. (—203° F.) Methyl 
alcohol (wood alcohol) was easier to freeze than 
ordinary alcohol. Phosphorous chloride froze at 
about —111°8° C.(—169° F.) These substances, it is 
claimed, were never frozen before this period 
(Wiedemann’s Annalen, 1883). ; 

The figures show that these liquids are not avail- 
able for low temperature thermometers, and are 
cited here for the purpose of showing that fact. 

The ordinary mercury and spirit thermometers, 
familiar to all, and their modifications, the carbon 
bisulphide and other themometers of liquid contents, 
then, are useless for very high or very low tempera- 
tures, their liquid contents volatilizing or freezing 


44 


Celsius 


Scale2728- 


- 180 


100 


30 


~100 


-150 


C 


r= 


LIQUID AIR (AND. THE 


Absolute 
Scale 


500 


450 


100 


350 


200 


150 


100 


Gas Thermometer 
of Varying Vol- 


ume, 


solid at high and low temperatures 
respectively. Air was substituted 
for the liquids, and thermometers 
operating by its expansion when 
heated were devised. . The cut 
shows the general features of con- 
struction of one of these. The bulb 
contains air at &. Mercury, J, lies 
in the tube, cutting off the end from 
the bulb. As “the air -expandsiig 
forces the mercury up; as it con- 
tracts, the mercury descends. This 
isa thermometer of changing vol-_ 
ume. It is not so satisfactory as 
the air thermometer of constant 
volume. 

The cut also shows the relation 
of the Centigrade and absolute 
thermometer scales. On the left is. 
engraved the Centigrade or Celsius 
scale, with its zero marked o at the 
point of melting ice, its 100° mark 
at the point of boiling water, and 
—273° at the absolute zero. On 
the right is the absolute scale, on 
which ice melts at 273° and water 
boils at 373°. 

There is a third thermometer 
scale which may be mentioned 
here, although it is rarely used in 
scientinc,; work:. it iscalledase ae 
Reaumur. The zero is the same as 
the Centigrade zero, and the boil- 


LIQUEFACTION OF: GASES. 45 


ing point is made to read 80°. This is the basis for 
its expansion up and down. At the absolute zero its 
reading 1s —218°4°. | 

If, as the temperature changes, a confined gas is 
kept at a constant volume, its pressure will vary; it 
will rise as the temperature rises and will fall as it 
falls. If we provide a means for measuring the 
presure of the confined gas, we can determine there- 
from its temperature. 

The word gas has been used instead of air, for 
other gases can be used with equal accuracy. For 
the extraordinarily low temperatures encountered in 
gas liquefaction investigations an air thermometer is 
useless, because the air hquefies. Just as mercury 
gave place to alcohol in liquid thermometers for low 
temperature work, so did air give place to hydrogen 
in gas thermometers. 

The constant volume hydrogen thermometer as a 
standard temperature-determining instrument for 
low temperature work is of simple construction, 
based on the phenomena of change of pressure under 
change of temperature in a gas kept at constant 
volume. This is the converse of the expansion and 
contraction of matter when heated. It is practi- 
cally only applicable to matter in the gaseous 
state. 

If a thermometer of the ordinary construction is 
heated until the tube is filled to the top by the ex- 
panding mercury or alcohol, a little more heat will 
crack the glass, and the contents will escape. The 
expansion of liquids when heated generates enor- 
mous pressures. But if the thermometer were filled 
with air or hydrogen or other gas, it could be 


46 LIQUID AIR AND THE 


heated very hot, probably to the melting point of 
the glass, before it would give way. 

In the mercurial, alcoholic or other thermometer 
with liquid contents, the heat is measured by the ex- 
pansion of the liquid, which is purposely so placed 
| as to be perfectly 
free to expand. In 
the air, hydrogen or 
other gas-filled ther- 
mometer of the type 
we describe, the gas 
is kept at constant 
volume, and the 
pressure it exerts is 
measured. A _ dia- 
grammatic repre- 
sentation of the con- 
R struction is given, 

which can be readily 
followed by the 
reader. 

A bulb, A, is filled 
with perfectly dry 
pure hydrogen. 
From its top acapil- 
lary tube; a, arises 

| and connects with 
Details of Hydrogen Thermometer, a mercury tube, 5S, 

The connection is 
preferably so made that the top of the mercury 
tube shall be perfectly flat. The capillary tube, d, 
enters a little to one side of the flat top of the tube, 
S. In its center a point, ¢, of glass, ivory, steel, or 


LIQUEFACTION OF GASES. 47 


some material unattacked by mercury, is attached, 
which points downward. 

The bottom of the mercury tube is reduced in 
diameter, is open, and an india rubber tube has its 
end thrust over it. The other end of the india 
rubber tube is connected to the bottom of another 
glass tube, k, termed the manometer tube. When 
the apparatus is set up, this tube can be moved ver- 
tically up and down. A clip moving up and down 
a vertical rod ona firm stand and attached to the 
tube enables this to be done. The tubes, #&: and 5S; 
contain mercury. 

If the tube, A, is raised or lowered to the proper 
point, the mercury in S can be brought to precisely 
the level of the point. This is indication by a point, 
a very delicate means of fixing the level of mercury. 
It is used in barometers in adjusting the level of the 
mercury in the cistern, and is taken as being sensi- 
tive to one-thousandth of aninch. The mercury as 
it rises reflects, mirror-like, the point. When the 
latter touches the mercury, the point and its re- 
flection form a continuous line. If the mercury is 
raised too much, a dimple forms on its surface. The 
appearance is unmistakable. 

By the manipulation of the observer sliding the 
manometer up and down the rod, the mercury is 
brought into accurate contact with the point, ¢. This 
is done for every reading of a temperature., This 
being the case, it is obvious that the heights of the 
upper surface of the mercury in R will vary accord- 
ing to the pressure of the gas in A. As this is 
greater, the surface of the mercury in~R will be 
higher; as the pressure is less, the level in & will 


4% LIQUID AIR AND THE 


be lower; the readings being taken only when the 
mercury in S has been brought to its exact level by 
raising or lowering the manometer tube, &. The 


ivan Thin 


Bi 


O mw 


AA 
he ea 
hi 


Hydrogen Thermometer. 


greater pressures  corre- 
spond to greater heat of 
the contents of the bulb, A, 
the lesser pressures to lower 
heat. By measuring the 
difference of level potmmaue 
surfaces of mercury, the 
data for calculating the 
heat are given. 

The height is best read by 
a cathetometer. This is a 
telescope with cross-wires 
across its tube, in the focal 
plane, and mounted to be 
moved up and down a 
vertical rod on another 
stand, without ever depart- 
ing from a perfectly hori- 
zontal position. A vertical 
scale of great accuracy of 
division is mounted near 
the manometer tube. The 
telescope is focused from 
a distance upon the appa- 
ratus. The mercury is ad- 
justed by moving the mano- 
meter tube until the mer- 
cury touches the point, e. 
The telescope is slid up 


and down until the image 


oe 


LIQUEFACTION OF GASES. 49 


of the surface of the mercury in the manometer 
tube, A, exactly coincides with the cross-wire as seen 
in the telescope. The telescope is now swung ina 
horizontal arc if necessary, until it takes the vertical 
scale into the field. The reading of the scale gives 
the height of the mercury. The same is done for 
the mercury in the tube, S; the difference gives the 
pressure of the hydrogen in units of a column of 
mercury. 

As the point, ¢, is supposed never to change posi- 
tion, the scale may be adjusted so that its zero is at 
the level of the point. Fora series of readings one 
reading of the point level would in any case suffice. 

The general mounting and disposition of parts of 
a constant volume gas thermometer are shown in the 
cut. A is the gas bulb, d the capillary tube, S the 
mercury tube, & the manometer, 7 J the frame, 
and & the vertical scale. Clamps are arranged to 
slide up and down the side rods of the frame so as to 
adjust the levels of the mercury vessel and mano- 
meter tube. 

Prof. H. Kamerlingh-Onnes, of Leyden, prepares 
hydrogen tor his hydrogen thermometer by electro- 
lysis as described in the most general terms on 
page 148. A very carefully constructed apparatus is 
used for the purpose. The interior of the hydrogen 
‘bulb and tubes are most elaborately cleaned with 
chemical solutions and distilled water and dried be- 
fore the introduction of the hydrogen, and various 
modifications have been introduced by him. 

At the risk of trenching upon the determination to 
avoid the introduction of much mathematics into 
this volume, the very simple calculation used in re- 


50 LIQUID AIR AND THE 


ducing the hydrogen thermometer readings to the 
standard is given. The reader may be assured that 
it is not as complicated as it appears. 

To obtain the formula for the thermometer, the 
bulb is immersed in melting ice or snow, and the 
manometer is adjusted so that the level of the 
mercury in S just reaches the point, ¢. (See cut on 
page 46.) The readings of the heights of the two 
mercury columns are now taken. 

The calculation is based upon equating two ex- 
pressions for the weight of hydrogen contained 
under the conditions of the two readings in the bulb. 
Let Sy) be the specific gravity of the gas in the bulb, 
let V, be the volume of the bulb, and ~ the volume 
of the capillary tube; let H’ be the height of mer- 
cury column, measured from the fixed level of the 
point, ¢, to the level of the upper surface of the mer- 
cury in the manometer tube increased by the height 
of the barometric column. S,is taken at 0° C. and 760 
mm. barometer. The weight then will be expressed by 


- Ely 
So | VG = Vo ———= 
76) 


Next the bulb is placed in the substance whose 
temperature-is to be. determined. Let 2 be vthe 
coefficient of expansion of hydrogen (0°00367), a that 
of glass, ¢ the temperature to be found, and H the 
new difference of levels of mercury columns increased 
by the height of the barometric column. The weight 
of hydrogen, the same as before, is 


I+aiz H 
Ik? 760 


LIQUEFACTION OF GASES. 51 
And equating we have: 


lot le gad H 
So Vo + YW) = So v; + a] == 
760 It+kt 760 


Solving these with respect to ¢, we find that— 
ey (Vo + %) (A—H’) 
V, (4 H’—a H)—  & (H—H’) 


This seems rather a complicated formula, but the 
use of the hydrogen thermometer is amply justified 
by the sensitiveness of the instrument, its great 
accuracy and great range. It can be used from the 
temperature of liquefied gases up to that of the 
melting point of glass. 

If two dissimilar substances have their ends con- 
nected so as to make a circuit, and if both are con- 
ductors of electricity, a current of electricity will 
pass through them as long as one of the contact 
points of the dissimilar substances is hotter or colder 
than the other. The effect is termed thermo-electric 
and the junction is termed a thermo-electric junction, 
The current with a single pair of junctions will be 
due to a very slight potential difference. The 
greater the difference of temperature, the greater will 
the potential difference be. If means are provided 
for measuring the potential difference, and if the 
temperature of one of the junctions is known, then 
the amount of the potential difference will give data 
for calculating the temperature of the other junction. 

The thermo-electric junction has been much used 
in low temperature work. The conductors may be 
varied a good deal.. A standard type is German 
silver—copper. The former metal is an alloy of 


52 LIQUID AIR AND THE 


Kamerlingh-Onnes’ 
Thermo-electric 
Thermometer. 


copper, nickel and zinc. Other 
couples are German silver—cop- 
per sulphide (Becquerel’s); Ger- 


‘man silver—zinc-antimony alloy 


(Noé’s); iron—bismuth-antimony 
alloy (Clamond’s). 

The ordinary practical unit of 
potential difference in electric 
work is the volt. In the thermo- 
electric junction the difference is 
so slight that it is usually meas- 
ured by micro-volts, or mil- 
lionths of a volt. The measure- 
ment of the potential difference 
is effected by means of a sensi- 
tive galvanometer. It is unne- 
cessary to give the details of this 
operation. 

As an example of the thermo- 
electric couple, as applied to the 
determination of low tempera- 
tures as encountered in the lique- 
faction of gases, an illustration 
of the couple used in the cryo- 
genic laboratory of the Univer- 
sity of Leyden is given. This 
laboratory, specially fitted with 
elaborate apparatus of the Pictet 
type, has won considerable fame, 
and, under the charge of Prof. 
H. Kamerlingh-Onnes, much 
excellent work has been done 


. there. ~ Ina, journal recently 


LIQUEFACTION OF GASES. 53 


started in Berlin, and which is devoted to the topic of 
compressed and liquefied gases (Zeztschrift fuer com- 
primirte und fluessige Gase), is given a description of 
the principal apparatus in the laboratory, which 
may be advantageously studied by those specially 
interested in the liquefaction of gases. 

The cut gives the section of the thermo-electric 
couple. It is formed of a straight German silver 
wire soldered at its lower end to a thin copper wire. 
The latter is coiled into a helix. 

The cut shows in the center the German silver 
wire as a straight black line. It lies within a glass 
tube. Around the outside of the latter is wound a 
thin silk-covered copper wire. The ends of the 
two are inserted into a block of copper and soldered, 
The silk insulation serves to keep the copper wire 
from touching itself in its successive turns. Another 
way of arranging it is to melt and wind a thin glass 
filament around the tube and wind the wire in the 
grooves it forms. 

Outside of the inner tube and of its winding of 
copper wire is a second glass tube. By india rub- 
ber tubing the junctions are completed as shown. 

The copper block at the bottom is turned off to a 
shoulder, so as to fit inside the outer glass tube. A 
thin tinned sleeve of copper is, soldered to it, and 
this sleeve goes outside the lower end of the outer 
glass tube. The joint is made good with melted 
sulphur. By the side branch the apparatus is filled 
with dry air, two apparatus being joined by a rubber 
tube for the purpose. 

By immersing the copper block in anything colder 
or hotter than the wires themselves are, a tempera- 


54 LIQUID AIR AND THE 


ture difference is established. One of the junctions 
of two dissimilar metals is at a temperature different 
from that of the rest of the wires and of the other 
junction. If the ends of the wires are connected in 
circuit with a galvanometer, it will be deflected by 
the current due to the thermo-electric effect. 

Such an instrument is calibrated by comparison 
with an air or hydrogen thermometer, and indicates 
changes of heat with great delicacy. A moment's 
reflection will show that where two dissimilar 
metallic or other conductors are joined, so as to 
form a circuit, there will be two junctions of dis- 
similar conductors; the circuit must include two 
thermo-electric junctions. The general law is that 
the electromotive force developed by a thermo- 
electric couple varies with the excess or depression 
of temperature of one junction over that of the other 
junction, which must lie in the rest of the circuit. 
This law holds measurably true for excessive varia- 
tions. For a German silver—copper couple, the 
potential difference is about one hundred-thousandth 
(o‘00001) of one volt per degree Centigrade, or five- 
ninths of this amount per degree Fahrenheit. 

Many substances possess the property of opening a 
path through the luminiferous ether for electricity. 
A constant discharge at very low potential can occur 
through sucha path. The discharge of electricity 
is called a current, the substance whose presence 
opens the path is termed a conductor. Copper 
wire is one of the best conductors known, and is 
very familiar in such application. House work 
for telephones, electric lights and electric bells is 
generally, almost universally, done with copper 


LIQUEFACTION: OF GASES. 55 


wire. It is rapidly being introduced on main tele- 
graph and long distance telephone lines. 

Electric conductors, like water pipes, may be good 
or bad conductors. A smooth-lined water pipe will 
carry or conduct more water than one with rough 
interior. Some metals will conduct electricity 
better than others. A metal of poor conducting 
power is said to have great or high resistance. 
Iron is of rather high resistance, platinum is of ra- 
ther high resistance, copper and silver are of low 
resistance. 

The same conductor varies in resistance with its 
temperature. Generally, the hotter it is, the higher 
is its resistance, and the colder it is, the lower is its 
resistance. It is believed that at the absolute zero 
of temperature, the resistance of copper or of iron 
would be abolished almost entirely or even entirely. 
Then the thinnest wire could conduct the horse 
power of Niagara to any distance without loss. 

Based on the above facts, the platinum wire 
resistance thermometer is constructed, and while 
it is also an instrument adapted for high tempera- 
tures, it has been used with the best results in the 
investigation of the low temperatures encountered 
in the investigations of liquid air and liquefied gases. 

Olszewski in an article in the Philosophical Maga- 
gine for 1895, claims that his associate, Witowski, 
was the first to successfully use the platinum resist- 
ance thermometer for the determination of liquefied 
gas temperatures. In its usual form it is very 
simple, such simplicity being possible because liquid 
air and the liquefied gases in which it is used are 
excellent insulators. * As the wire is to be surrounded 


56 LIQUID AIR AND THE 


by them, the fact that it can be immersed uninsulated 
without short-circuiting conduces to simplicity of 
construction and to sensitiveness. 

The principle of construction can be seen in the 
cut, in which is given a representation of an appa- 
ratus used by Prof. Dewar to show the decrease of 
resistance of a wire when the temperature is lowered. 
The tube is a vacuum tube containing liquefied oxy- 
7 gen or liquid air. In it is im- 
mersed a coil of fine platinum 
wire, held in shape by a sheet of 
mica with notched edges, around 
which itis wound. Two heavy 
| platinum wires serve as connect- 
ors. These are so large in dia- 
= meter, and so short, that their 
| | resistance may be regarded as 
\ quite negligible. The wire with 
the mica sheet and its mounting 
is the thermometer. 

Another form of construction 
provides for a more thorough 
exposure of the platinum wire 

ane to the changes of temperature 
Sar eie ee by separating it as far aS possi- 
A vnrniometen ble from contact with other mat- 
ter than the liquefied gas. Out 

of very thin mica, or ebonite a frame is made whose 
cross-section is a sort of hexagonal star. Around 
this the platinum wire is wound. This arrange- 
ment provides a coil of wire in contact with a non- 
conducting substance only at a comparatively small 
number of points, six for each complete turn of the 


(r 


iii 


SS 


-LIQUEFACTION OF GASES. By 


coil. It isa disposition of the wire which secures a 
considerable length in a small space, and which 
leaves the wire free to be in most intimate contact 
with the material surrounding it. The temperature 
of the wire changes with the greatest quickness, and 
the thermometer is of the most sensitive type yet 
devised. It is due to Prof. Olszewski. 

The platinum wire he employed was o'025 milli- 
meter, or about one-thousandth of an inch in diame- 
ter. The successive turns of the wire were one-half 
to one millimeter, or one-fiftieth to one twenty-fifth 
of an inch distant from each other. 

Witowski’s electric resistance .-hermometer was 
constructed with a view to keeping the platinum 
wire out of contact with the liquid it was to be im- 
mersed in. The wire was wound upon a copper 
cylinder with mica insulation. It was inclosed in a 
copper foil cylinder, and was hermetically sealed 
therein. 

Callendar and Griffiths studied the subject of pla- 
tinum resistance thermometers in the Cavendish 
Laboratory, at the University of Cambridge, Eng- 
land. They reached the conclusion that the instru- 
ment is accurate to one-thousandth of a degree 
change of temperature. This fact, together with its 
great sensitiveness, makes it an ideal instrument for 
use with non-conducting liquids such as liquid air. 

The thermometers are used by passing an almost 
infinitesimally small current through them and 
accurately measuring the resistance. It varies in 
degree with the temperature, and the instrument 
may be standardized by the hydrogen thermometer. 

Finally, there is one more way of determining 


58 * LIQUID AIR AND THE 


what may be termed extreme temperatures, which 
was tested by Cailletet in some of his recent work, 
which showed that it was reliable for liquefied gas 
temperatures. A piece of metal of known weight 
and specific heat is immersed in the liquid whose 
temperature is to be determined.» —Atter sits has 
attained the temperature, in five minutes, more or 
less, it is removed and transferred to a calorimeter or 
apparatus for determining the quantity of heat in it. 
The simplest calorimeter is a vessel of water, and for 
rough work this can be used. The piece of metal 
is quickly thrown into a vessel of water of known 
weight and temperature. The change of tempera- 
ture of the water brought about by the introduction 
of the piece of metal, by a simple calculation gives 
the temperature of the piece of metal. 

For scientific work some of the more accurate 
forms of calorimeter are used, which it is unnecessary 
to describe here. The calorimeter method has been 
very rarely used, and is only mentioned here on 
account of Cailletet’s paper of 1888. 


LIQUEFACTION OF GASES. 59 


GRAB PEAR ELE 
HEAT AND GASES. 


The perfect gas—The ultra-perfect gas—Energy expended in 
heating a gas—Specific heat at constant pressure and at 
constant volume—Atomic heats and variationsrof same 
from equality with each other—Adiabatic and isothermic 
expansion of gases—Carnot’s cycle—The perfect heat 
engine—Available and unavailable energy—Unavailable 
energy rendered available by liquid air—Latent heat of 
melting, of vaporization, of expansion—Boiling a cooling 
process—Expansion a cooling process—The spheroidal 
state—The Crookes layer—Experiments and _ illustra- 
tions—Utilization of the spheroidal state in low tem- 
perature work and in liquid air investigations. 


The perfect gas has certain defined characteristics, 
or it may more properly be said, should have them ; 
for a perfect gas is a rarity, and some of the repre- 
sentative methods of liquefying air are supposed 
to be based on the fact that air is not a perfect 
gas. 

If a gas is compressed, energy is expended upon it 
and an equal amount of energy is developed in the 
gas. This appears largely and principally as heat. 
Were air a perfect gas, it would all appear as heat. 
But in the case of air at 19 atmospheres, about #5 
of the energy spent in compressing it fails to show 
itself as heat energy. 

Following this out, a perfect gas expanding against 
pressure and developing energy should lose heat 


60 LIQUID AIR AND THE 


exactly equal to the energy it expends in the ex- 
pansion. But here, too, there is a loss of heat 
energy. The expanded air is a little cooler than it 
ought to be, because the act of expansion requires 
energy to be spent upon the molecules in some not 
well understood way. Hence there is a greater 
_ cooling than would be indicated by the energy ex- 
pended. 

Hydrogen is a gas that acts in the opposite way. 
It requires more energy to compress it than would 


Vacuum 


— AirA B 


Joule’s Experiment. 


be indicated by the heat developed, and in its ex- 
pansion it does not get as cool as it ought to. 
Hence it is a more than perfect gas—an ultra-per- 
fect gas. | | 

There is no perfect gas known. None has ever 
been found capable of standing the tests which a 
perfect gas should respond to. | 

One test to which a perfect gas should respond is 
the following: Two gas receptacles are connected 
by atube. One is charged with gas under pressure, 
the other has a vacuum produced within it. A cack 


LIQUEFACTION OF GASES. 61 


upon the pipe connecting them is closed so as to 
maintain the condition described. The two con- 
nected vessels are immersed in water and all is left 
standing until the gas receptacles, the gas in one of 
them and the water surrounding them, are of even 
temperature. Now the gas cock is opened. 

The compressed gas streams out of the one recep- 
tacle into the other. As it expands it exerts mechan- 
ical energy. This must be supplied from some 
source, ahd heat energy is called upon. The ex- 
panding gas grows cooler. The gas in the other 
vessel is compressed. Energy is developed and must 
show itself ; it appears as heat. The gas in the second 
vessel is heated. 

If the gas were a perfect gas, the heating would 
exactly balance the cooling, and the temperature of 
the water would be unchanged. Joule tried the ex- 
periment, and thought that the temperature of the 
water was unchanged. There was so little altera- 
tion that it completely escaped recognition; a ther- 
mometer with bulb immersed in the water was 
apparently unaffected. But there was a difference. 
If air was used, the temperature would fail, and the 
same is to be said for most other gases. 

These differences are so slight that it is only by 
delicate tests that they can be detected. The scien- 
tific incredulity of Joule and Thomson led them to 
try a simple experiment, which may be described 
here. 

A tube is provided with an air-tight piston. A 
diaphragm extends across its center. This dia- 
phragm is made of a porous material which will only 
permit the passage of air with some difficulty. If 


62 LIQUID AIR AND THE 


the piston is forced in, the air is compressed and 
heated. It escapes through the pores in the piston 
and expands as it escapes. Now, as the expansion 
of the air exactly undoes the compression, there 
should be an exact balance of energy expended on 
the air on the piston side and energy expended by 
the air on the free side. Hence, the escaping air 
should be of the temperature of the atmosphere. 
But it is found to be lower. Air is an imperfect 
gas. If hydrogen be substituted for air, the temper- 
ature is higher. Therefore, hydrogen is an ultra- 
perfect gas. 
- Ourancestors had their own way of looking at 
gases. They at- 
N tempted to classi- 
\ oe c fy them into per- 
N manent and non- 
Joule’s and Thomson’s Experiment. permanent gases, 
for they believed 
that there were some gases which could not by any 
degree of cold or pressure be liquefied or solidified. 
These they called permanent gases. Then there was 
adopted a rather crude division of gases and vapors. 
The latter were easily reducible to the liquid form, 
the former were not. This was profoundly unscien- 
tific and inexact. It left it largely a matter of fancy 
when a gas should be called a vapor. It led to con- 
fusion of ideas, and such expressions as vapor den- 
sity, tension of aqueous vapor, and the like have 
done much to obscure the student’s view of the 
status of things. But it is uncertain when the terms 
which have more or less had this effect will have 
better ones substituted for them. Perhaps it 


LIQUEFACTION OF GASES. 63 


may be that it will be hard to find better expres- 
sions. 

The best definition of a vapor is. perhaps, the 
following: A gas which, by the least increase of 
pressure or reduction of temperature, would be re- 
duced, in part, to a liquid. The term vapor, thus 
defined, is subjective. If a liquid is introduced into 
a vacuum, it evaporates in whole or in part. If 
enoughis introduced, an excess of liquid may be leit, 
and will lie on the bottom of the vacuum chamber. 
The gas filling the chamber is then a typical example 
of a vapor as thus defined. 

In the upper part of a barometer tube there is 
present volatilized mercury, mercury gas or vapor, 
in exceedingly small amount. ‘This varies in amount 
with every change of temperature and of barometric 
pressure. In the outer chamber of Dewar’s bulbs 
for holding liquid air a globule of mercury is seen. 
This fills the vacuous space with mercury gas or 
vapor. These are examples of vapor as defined 
above. 

In the present work an endeavor will be made to 
adhere to the term gas, to the exclusion, as far as 
possible, of the term “vapor.” As we have little to 
do with chemistry, the subject of gases will be com. 
paratively simple, as they will be dealt with as 
physical concepts. Thus, although air is a mixture 
of two principal gases, oxygen and nitrogen, with 
smaller amounts of others, such as argon, gaseous 
water, and carbonic acid gas, it will be spoken of as 
a gas when only its physical relations are under con- 
sideration. 

Another definition of vapor is, a gas at any tem- 


64 LIQUID AIR AND THE 


perature below its critical one. It is a gas which by 
pressure alone can be reduced to the liquid state. 

However little one may fancy the term vapor, 
owing to the varied definitions given for it, there are 
some cases when its use is almost obligatory. Water 
vapor is one of these. If we speak of water gas, it is 
taken to indicate a combustible gas, containing free 
nydrogen, but no water, which is produced by 
passing steam through incandescent coal or other 
carbonaceous material. Therefore, as the chemist 
calls carbon monoxide, incorrectly, carbonic oxide, 
simply to avoid confusion incident to the attempt to 
supersede a long standing error in terminology, we 
may, and almost must, adhere to the term water 
vapor. 

A gas may be heated so that it will expend energy 
on account of the heating. This takes place if it is 
allowed to expand. Hence the heat required to 
raise the temperature of a gas free to expand 
involves two offices to be performed. A substance, 
which is the gas in question, is to be heated. This 
requires one portion of the heat. Thenenergy has to 
pe supplied to the gas to enable it in turn to expend 
energy onits own expansion. This requires a second 
portion. 

If the gas is confined so as to be incapable of 
expansion, the temperature can be more readily 
raised. The gas is inert and merely represents a 
mass to be heated. Less heat is required than in the 
case where the gas expands. 

if it took a quantity of heat energy represented 
by 1 to heat a given weight of unexpanding gas a 
given amount, to heat the same weight of gas the 


LIQUEFACTION OF GASES. 65 


same amount, when the gas is free to expand under 
its effect, would require a quantity of heat energy 
represented by 1°4058. 

The quantity of heat required to heat identical 
weights of different solids, liquids or gases under 
identical conditions varies. The relative quantities 
required are termed the specific heats of the sub- 
stances in question. The two kinds of specific heats 
of gases which have just been described are termed 
specific heat under constant volume and _ specific 
heat under constant pressure. 

The same two kinds of specific heats exist for 
solids and liquids. The expansive force exerted by 
the latter when heated is so enormous that there is 
no practical way of accurately determining the spe- 
cific heat at constant volume of most liquids or solids, 
because neither can be kept at a constant volume 
except in a very few instances. 

Specific heat is, as has been said, the relative quan- 
tities of heat required to produce an identical change 
in temperature in equal quantities of different sub- 
stances. The laws of specific heat vary in the cases 
of matter in the solid, liquid or gaseous state, and 
also vary with the temperature. In liquids and 
solids there is no approach to regularity. Water is 
taken as the standard, and the specific heat of liquids 
is stated by weight. Water has a very high specific 
heat. Mercury, for instance, has but approximately 
one-thirtieth the specific heat of water. A pound 
of water at a high temperature would have as much 
heating power in its cooling as would thirty pounds 
of mercury. 

When we come to elements, we at once find a law 


66 LIQUID AIR AND THE 


which is approximately followed. If we multiply 
the atomic weight of an elementary substance, such 
as gold, silver, lead, etc., by its specific heat, we get 
a number which is almost constant for all of the solid 
elements. This indicates that the heat required to 
heat an atom of a substance a given amount is ap- 
proximately the same, of whatever element the 
atom may be. 

The atomic weights of elements represent the 
relative weights of single atoms of the bodies in 
question or of equal numbers of atoms. It follows 
that if we take the ordinary specific heats, which are 
referred to equal weights of the substances, and 
multiply them by the atomic weights of the respec- 
tive elements, the product will give the specific 
heat referred to, the heating of weights correspond- 
ing to the weights of the atoms. 

These products are termed the atomic heats, and 
they vary but slightly among themselves. They are 
so nearly the same that a law was enunciated by 
Dulong and Petit to the effect that the atomic specific 
heats of the elements are identical. 

Like many other enunciated laws, it does not hold 
true. The products given by the required multipli- 
cations vary from 5°39 to 6°87, and it is not easy to 
reconcile one’s self to the idea that the differences are 
due to experimental error. The law is best accepted 
as being, like many other natural laws, only approxi- 
mately true, and as being a useful instrument in 
determining certain chemical constants. 

There are two expressions in constant use in 
thermodynamics which should be explained in this 
book, as they occur in discussions of the problems of 


— —— 


LIQUEFACTION OF GASES. 67 


expansion and contraction of gases. Once explained, 
the explanation may be easily remembered as being 
descriptions of near relatives of the two specific 
heats which have been described. The two specific 
heats were specific heat at constant volume and 
specific heat at constant pressure. The two expres. 
sions to be explained are OSH wit Oe IE 
expansion or contraction. Canuistd | a “Ke 

Suppose that a gas is placed ina sspidioH which 
permits it to expand. The molecules repel each 
other, they beat back and forth constantly, striving to 
augment the length of the paths they move over, so 
if the conditions permit expansion, the gas expands. 
In expanding it will exert energy, and the energy 
has to be supplied from some source. If none is 
supplied from an external source, the gas will fall in 
temperature, the encrgy will be drawn from the in- 
herent heat of the gas itself. Imagine the almost 
theoretic case when the gas expands thus absolutely 
at the expense of its own heat. No heat has been 
added to it, the expansion is adiabatic. 

The condition rarely exists in practice, except in 
approximation, because as we work with gases under 
confinement, there isa surrounding vessel of more or 
less heat-conducting material, the gases pass through 
pipes and valves, and are in constant contact with 
objects at various temperatures.. But one case exists 
in which a gas is compressed without the use of any 
restraining or impelling mechanism, without piston 
~and cylinder, and where the expansion is so rapid 
and of such short duration that the adiabatic condi- 
tion is almost exactly obtained. It occurs in the 
sound wave. 


68 LIQUID AIR AND THE 


When a sound is made in a gas, waves start from 
the center of sound disturbance, and travel through 
space at the rate of abouta thousand feet a second. 
In a second there may be anywhere from nine or ten 
waves up to twenty or more thousand such waves 
within the range of human audition. Each wave is 
composed, not of up and down motions, as in a wave 
on the sea, but of a forward impluse of the particles, 
followed by a springing back. On the forward im- 
pulse the air is compressed; on the reverse impulse, 
expanded. The action is very brief in duration and 
very slight, but the expansion and compression are 
practically adiabatic. 

The air is surrounded by no containing vessel, 
and is condensed against its own inertia, so that 
every disturbing condition is absent, such as metal 
or glass to be heated, and the shortness of the pe- 
riod contributes to the perfection of action. The 
phenomena of the propagation of sound in air are 
used to deduce the factor 1°4058 (page 65). The de- 
termination is based upon the assumption that air 
in the sound wave expands adiabatically. 

Now suppose that the gas expanded just as before, 
except that we added heat to it, so that as it expand- 
ed it kept exactly the initial temperature. If it was 
air expanding in a cylinder, we might have a fire 
heating the cylinder. The air would absorb heat as 
it expanded without rising intemperature. Although 
the expression is not generally applied to such a 
case, the heat would be as truly latent heat as is the 
heat of liquefaction or of vaporization.. We might 
start with 1 cubic foot of air at a temperature of 
100° and end with 2 cubic feet of air at the same 


LIQUEFACTION OF GASES. 69 


temperature. Our fire would do the work of pre- 
venting an adiabatic fall-of temperature. 

Such expansion is called isothermic expansion. 

Opposed to expansion is contraction. There is an 
adiabatic contraction in which a gas yielding to ex- 
ternal energy diminishes in volume without impart- 
ing to anything the heat given it by the energy ex- 
pended on it. It-grows hotter. . If the action is 
theoretically perfect, if it gives off absolutely none 
of the heat energy into which the mechanical energy 
exerted upon it has been converted, the contraction 
is adiabatic. 

But the vessel in which the air is compressed may 
be cooled artificially, so as to keep the air at precisely 
the same temperature. A stream of water may cir- 
culate through a water jacket surrounding the 
vessel. The water may be assumed to absorb the 
heat. The contraction is isothermic if the cooling is 
so complete that no rise in temperature takes place. 

The primitive idea of a steam engine, if we except 
Hero’s reaction engine, is represented by a piston 
and cylinder. A little water is placed in the cylinder 
and under the piston and is boiled. The steam forces 
the piston upward. At the end of the stroke, the 
steam is cooled and condensed to water and the pis- 
ton descends. 

Now, to avoid complication, imagine the steam re- 
placed by air. The air is heated. It expands, and 
heat is constantly applied till the stroke is partly 
completed, so as to keep the air at the same temper- 
ature. This much of its expansion is isothermic. 
Next it is left to itself, and without receiving any 
more heat, expands until the end of the stroke is 


7O LIQUID AIR AND THE 


reached. This is adiabatic expansion. It now re- 
turns or performs the return stroke, the first portion 
by isothermic contraction, the air being cooled and 
kept cool, and completes the return stroke by 
its own contraction, with ensuing rise of tempera- 
ture, or by adiabatic contraction. We will assume 
it to return to exactly the temperature it started at 
before it was heated at all. 

The course of operations started with the air at a 
given volume and temperature, it went through a 
cycle of changes, and returned to its original volume 
and temperature, thus completing the cycle. To 
carry it out, conditions impossible of realization 
would have to be obtained. No engine could be 
built which would give the cycle perfectly. 

An engine operating thus by expansion and con- 
traction of a gas isa reversible engine. The steam 
engine is a typical example. The gas engine is an- 
other. 

The cycle is termed Carnot’s cycle, and the suppo- 
sititious engine that would carry it out is called 
Carnot’s engine. Such a cycle represents the most 
economical conditions under which power can be 
generated by heat. But the engine will never be 
built. - 

By following out the theory of Carnot’s cycle, we 
reach the following law, the famous second law of 
thermo-dynamics : 

In a reversible heat engine, the efficiency is re- 
presented by a fraction whose numerator is the 
range of temperature included in the operation of 
the engine, and. whose denominator is the highest 
temperature included therein. These temperatures 


LIQUEFACTION OF -GASES. 71 


must be expressed in the absolute scale of temper- 
ature. 

The law is all-important; directly or indirectly, it 
crops up constantly in the mechanics of the liquefac- 
tion of gases and of heat. 

It has been stated thus: 

Heat cannot of itself pass from a colder body to a 
hotter one, nor can it be made so to pass by any in- 
animate material mechanism, and no mechanism can 
be driven by a simple cooling of any material object 
below the temperature of surrounding objects, 
(Daniell.) 

Another way of putting it is: 

If the absolute temperature of a uniformly hot 
substance be divided into any number of equal parts, 
the effect of each of those parts in causing work 
to be performed is equal. (Rankine.) 

If we indicate absolute temperature by 9, and let 
6 and © indicate two temperatures, ©' being the 
higher, the second law states that in a reversible 
heat engine— 

, G1 — & 


Efficiency —= 
1 


Mechanical energy can be expended and can de- 
velop heat energy, but heat energy can never de- 
velop in the mechanical form but a portion of its own 
quantity of energy’ More and more mechanical 
energy is being convertcd into heat energy, and 
~ only a small portion can ever be recovered. Every- 
thing in the world tends to get to the same temper- 
ature; equalization of temperature is constantly 
taking place. In the existence of coal and air we 


72 LIQUID AIR AND THE 


have a form of potential energy, a potential high ~ 
temperature. But even this potential high temper- 
ature 1s disappearing as coal is burned up. The 
available energy of the world gets less and less. 
~The total energy is invariable. 

The second law of thermo-dynamics leads us to 
the same conclusions as does the doctrine of the con- 
servation of energy, although in this lowering of the 
scale of the world’s energies, and the rendering them 
unavailable by man, there seems to be involved a 
contradiction of conservation of energy. But en- 
ergy is intact in amount; in lowering its pitch, as 
we may express it, it ceases to be utilizable by man. 

Liquid air, once produced, enables us to utilize 
heat which otherwise would be unavailable. The 
trouble is that to produce liquid air we have hitherto 
been obliged to expend a great deal more available 
energy than we can utilize of normally unavailable 
energy by its gasification. 

Matter, as it exists in three states, solid, liquid and 
gaseous, is subject to two changes of state. Melting © 
is one of these changes, when it changes from the 
solid to the liquid state; vaporization is another, 
when it changes from the liquid to the gaseous 
state. 

Energy has to be used to bring about such changes 
of state, and no insignificant amounts, but very large 
amounts, relatively speaking, must be expended to 
effect the changes. Such energy is usually applied in 
the form of heat. If we wish to apply energy to a 
lump of ice and change it to the liquid state, we place 
it in a vessel upon a hot stove. If we wish to apply 
energy to the water so produced and change it to 


LIQUEFACTION OF GASES, 73 


the gaseous state, we keep it on the stove, and pres- 
ently it boils. 

By measuring the heat applied, it is found that 
a great deal is required to change the solid into a 
liquid and the liquid into a gas. This is not all. 

If we put a lump of ice into water, the water 
always takes the same temperature and keeps it until 
the last bit of ice is melted, provided that time is 
given for the water to assume the given tempera- 
ture. We may apply heat to the water. If it were - 
plain water, or if it were water with some unliquefi- 
able solid floating in it, such as a lump of cork ora 
block of wood, every addition of heat would show 
itself in a rise of the thermometer. But as long as 
the ice is floating about in it the water will be prac- 
tically unchanged in temperature, and will come 
back to the original temperature from any slight 
departure therefrom, as soon as taken from the fire, 
so that the ice has time to act upon it. Suppose we 
have put a pound of ice into the vessel. To melt it 
will require as much heat as would raise a pound of 
water nearly to the boiling point. 

Imagine a pound of ice just ready to melt put into 
one vessel and a pound of water into another. If 
both were equally hot, their temperature would be 
ep ©. (32 F:) Now imagine ‘exactly the same 
amount of heat applied to both until the ice was 
completely melted. We started with a pound of ice 
ato° C. Weshould find at the end of the process that 
we had a pound of water at exactly the same tem. 
perature in the place of the ice. Meanwhile what 
would have happened to the water in the other ves- 
sel? It would have become so hot that the hand 


74 LIQUID AIR AND THE 


could not endure the heat. It would have taken a 
temperature of 80° C. (176° F.) 

We have seen that our forefathers were not so 
fond of the term energy as we are. The ideas of the 
scientific world were not so well formulated as now, 
and the inevitable result followed that there was 
more complexity grafted upon the natural order of 
things than was necessary. They found that a 
quantity of heat was required to melt ice, and that it 
melted it without raising the temperature. The tem- 
perature would only begin to rise after the ice was 
melted. So they said the heat lies hidden; as it did 
not show itself on the thermometer scale, it must be 
concealed from us. They called it Latent Heat, 
which means hidden heat. 

A similar, but more pronounced, disappearance of 
heat takes place when water is made into gas, when 
we boil it in a kettle or boiler. The heat required to 
convert a pound of water into steam at atmospheric 
pressure would raise the temperature of ten pounds — 
of water 54° C. (97:2° F.) Suppose that the water 
we proposed to boil off had the temperature of 
46° C. (115° F.) when we started. This would be 
a heat which the hand could comfortably bear. 
Then it is obvious that after enough heat had been 
applied it would reach the temperature of 100° C. 
(212° F.) A thing heated is supposed to grow 
hotter, and our water would act as it ought to do. 
But once the temperature of 100° C. (212° F.) was 
reached, the water would no longer grow hot. It 
would stay at the temperature named, it would 
begin to boil, and would gradually grow less and 
less in volume, and without the heat increasing, each 


LIQUEFACTION OF GASES. 75 


particle would require ten times the heat expended 
on its preliminary heating to be converted into 
steam or gaseous water. The temperature of the 
steam, however, would be 100° C, (212° F.) 

These are examples of the two most prominent 
latent heats, the latent heat of fusion and of vapori- 
zation. The term is so convenient that it will be 
used for a long time to come. The better term 
would be the energy of melting or of fusion and the 
energy of vaporization. 

When a gas expands, it practically always expends 
energy and grows cold. Therefore, in the expansion 
of a gas under ordinary conditions, a loss of heat 
occurs, so that a_third kind of latent heat may be 
assumed to exist, the latent heat of expansion against 
pressure. This, however, is an expression not much 
used, and it is in the relation of specific heats at con- 
stant volume and at constant pressure that the con- 
ception finds its nearest expression. 

We use ice to cool our drinking water, and per- 
haps never give a thought to the phenomena mani- 
fested. Yet it is very impressive to see how a small 
lump of ice can cool a large pitcher of water. In 
melting, it can reduce four times its own weight of 
water from the temperature of a living room to that 
of freezing, and as long as a particle of ice is left, the 
water will remain cold. A lump of ice, weighing 
one hundred pounds, lasts for a long time in a refri- 
gerator. It absorbs as much heat in melting as 
would heat a ton of water through several degrees 
of the thermometric scale. 

If circumstances are such as to produce vaporiza- 
tion at ordinary temperatures, the substance vapor- 


76 LIQUID AIR AND THE 


ized must absorb heat energy. A cloth wet with 
alcohol dries rapidly, because alcohol vaporizes or 
is converted into gas at ordinary temperatures. 
Heat is absorbed, and the cloth becomes very cold. 
In the tropics drinking water is kept in porous 
vessels. It exudes to the surface and evaporates 
therefrom. Heat is absorbed in the process, and the 
water gets cool. A workman employed in steel 
works cannot endure the heat of the furnaces and 
metal until he perspires heavily, and then he is com- 
fortable. Irrespective of the physiological aspect 
of the case, the heavy perspiration by the heat © 
energy absorbed in its evaporation keeps the skin 
from scorching. If he ceases from any cause to per- 
spire profusely, he has to stop work until the sudo- 
rific glands begin to work once more. 

Evaporation, which is slow boiling, here effects a 
cooling of the water and of the perspiring work- 
man. 

The term “boiling ” is so firmly rooted in the mind 
as an expression of heat that. it is a little hard to 
think of it as indicating cold. Repeatedly we read 
of experimenters with liquefied gases using a vacuum 
so as to make a gas boil and thereby produce cold. 
One might think that anything which would make a 
gas boil would be heat. 

If what has been said about latent heat has been 
read and understood, it will be seen that boiling is a 
cooling process. If we wet the finger and hold it in 
a draught it becomes cold, because the water evapor- 
ates or boils off. This is a practical proof. But if it 
were possible to heat water so that it would not boil, 
the temperature of a pound of water would rise close ° 


LIQUEFACTION OF GASES. 77. 


toa red heat if enough heat were applied to it to boil 
it away under ordinary conditions. In other words, 
boiling keeps water relatively cool; it cannot get 
hotter under atmospheric pressure than 100° C. 
pone el ;) 

The way in which water is made to boil is usually 
by applying heat toit. A very familiar old experi- 
ment may be cited where cold is applied, producing 
a vacuum, and the simple vacuum causes strong 
ebullition. A round-bottom flask is half filled with 
water, and it is brought to the boil and kept so until 
the upper half of the flask is full of steam. It is re- 
moved from the source of heat, allowed to come to 
rest, and is then tightly corked and inverted. Cold 
water is poured over it. This condenses the steam, 
and forms a partial vacuum. The water which was 
quiescent now boils with great energy, because of 
the reduction of pressure, and its own temperature 
falls. If a thermometer had its bulb immersed in 
the water, a reduction of temperature would be in- 
dicated. 

It is obvious that this application of a vacuum is a 
means of lowering temperature. It lowers it by 
causing water to boil, so that we find the boiling of 
water a synonym for cooling or reduction of tem- 
perature. 

Substitute liquid ethylene, liquid air, or other 
liquefied gas for water and apply a vacuum. The 
liquid will boil with increased energy and vigor, and 
its temperature will fall. A boiling gas is a cooled 
gas and is used as a cooling or refrigerating agent. 

No one ever thinks of boiling a gas by imparting 
artificial heat to it. It is done either by exposing it 


78 LIQUID AIR AND THE 


to the atmosphere or by exhausting the vessel in 
which it is contained. The exhaustion makes it boil 
harder than ever. Exposure to the temperature of 
a boiling gas is exposure to cold. The more intense 
the boiling is, the greater is the cold. This expresses 
the condition of things obtaining in the work we are 
to describe. 

If we speak of a thing being exposed to the tem- 
perature of boiling oxygen, at atmospheric pressure, 
it is very cold; if to the temperature of oxygen 
boiling under exhaustion, it is still colder. If we 
speak of a gas being made to boil, it means that we 
apply exhaustion, and that its boiling is a synonym 
for its growing colder. The student of this subject 
must therefore associate boiling with coidness, and 
get rid of its oid association with heat. He must 
realize that boiling is a cooling operation, that if it 
did not boil, the water in a tea-kettle would get 
several times hotter than it can in fact. 

The spheroidal state of matter forms so important 
a subject, in connection with the liquefaction of 
gases, that it should be well understood by the 
reader. It is to our vision a very peculiar condition 
into which liquids sometimes enter. In reality it is 
their normal condition, and the reason it seems to us 
peculiar is because the conditions for breaking it up 
are so very generally present. 

In a liquid there is a slight force of attracticn be- 
tween the molecules. Hence the interior molecules 
are drawn to one another and are subjected to equal 
pulling stresses in all directions. On the outside 
or on the surface of a liquid, the molecules are 
pulled right and left and inward. Hence the outside 


LIQUEFACTION OF GASES. 79 


is in a state of strain and constantly wants to become 
of as small area as possible. By an elementary pro- 
position of geometry we can prove that of all solids 
of equal volume, the sphere has the smallest super- 
ficial area. Hence, if a mass of liquid is perfectly free 
from all external influences, the outer surface, under 
the effects of the lateral pulling that goes on among 
the molecules, will shrink to the smallest possible 
area by drawing the liquid into the shape of a sphere. 

A liquid so situated that it is drawn by its own 
surface film into a shape approximating a sphere is 
said to be in the spheroidal state. The surface film 
composed of molecules acts exactly tike a thin mem- 
brane of india rubber. 

When a liquid touches no solid or liquid, it 
takes the spheroidal shape. The free portion of a 
drop of water, dependent from a rod, is drawn by its 
enveloping film into a spheroidal shape. If another 
rod touches it, the spheroidal shape where they 
meet is destroyed. When a solid is wet by a liquid, 
it is because the molecules of the liquid have a 
greater attraction for the solid than they have for 
themselves. Hence the skin-like action of the outer 
layer of molecules is destroyed when a solid which 
the fluid can wet is brought into contact with them. 

Mercury wets very few substances. When thrown 
upon a non-metallic surface, or upon a metallic sur- 
face of iron or of some metal which it cannot wet, it 
forms, as it is scattered about, a quantity of minute 
globules. Each seems to be a minute ball rolling 
spout ireely, . Yet they are. perfectly liquid. ~The 
surface tension, or the elastic pulling of their surface 
layer of molecules, draws them into an approxi- 


80 LIQUID AIR AND THE 


mately spherical form. If mercury. is dropped 
upon silver, the spheroidal tendency is no longer 
discernible, because it makes a true contact with the 
silver, which destroys the spheroidal state. 

If a liquid is placed upon a surface very much 
hotter than itself, it slowly evaporates, and the pro- 
ducts of its evaporation form a sort of cushion 
upon which it hes out of contact with the hot sub- 
stance. The formation of this cushion of vapor. or 
gas is interesting. It forms what is known as a 
Crookes layer. It is named from Prof. William 
Crookes, of England, who discovered the character- 
istic phenomena of gases at high rarefactions. 

When gases exist in the condition in question, 
which condition is sometimes called the radiant 
state, they are in so rarefied a state that their mole- 
cules, in their vibrations, rarely collide. <A billiard 
ball pursues normally a straight course from cushion 
to cushion, unless it collides with another ball. 
This is what the molecules of a gas do. They keep 
a straight path until deflected from it by collision 
with other molecules. If a silver dish is heated 
quite hot, and a drop of water is placed in it, the drop 
becomes warm and evolves steam. The molecules 
of steam from its under surface, under the influence 
of the hot vessel, become hot and beat back and 
forth from drop to vessel. This distance is so small, 
and the paths of vibration of the molecules are so 
long on account of the heating, that very few col- 
lisions occur. The molecules simply repeat their 
paths up and down from drop to dish, and thus 
form a cushion which prevents the water from 
touching the dish. The water is drawn into an 


LIQUEFACTION OF GASES. SI 


approximately spherical shape, and the spheroidal 
state appears. 

The cushion formed by the non-colliding mole- 
cules is termed a Crookes layer. Because the mole- 
cules do not collide there is no tendency to drive 
the steam out laterally. There is probably a very 
small proportion which escapes at the sides. The 
diagram gives the ideal | 
section of a drop of 
water resting ona 
Crookes layer. The real 
layer is exceedingly thin. 
The distance between 
water and vessel may be termed infinitesimally 
small. 

A very homely simile would be afforded by a 
moving crowd. A man might elbow his way 
through it, and thereby thrust people to the right 
and left. But if the crowd was sparse enough, he 
would go right through it without pushing anyone 
laterally. In the Crookes layer the crowd of mole- 
cules is so sparse that the molecules do not hit 
and elbow each other. Therefore, there can be no 
side pressure, and the cushion of steam, in the 
experiment cited, stays under and supports the 
water. 

It might be said that ordinary steam would form 
a cushion or layer between the water and hot metal. 
But it would not, because the weight of the water 
would squeeze it out and the water would touch the 
hot metal and would boil violently. But it is 
obvious that in a Crookes layer, where the particles 
of molecules do not collide, there is no possibility of 


Theory of Spheroida! State. 


82 LIQUID AIR AND THE 


their being squeezed out sideways, as there can be 
no side push upon them. 

The experiment, as usually shown at lectures, is 
thus performed: A thick metal cup, preferably of 
silver, although brass is almost as good, is heated 
nearly or quite to redness. Water is now poured 
into it. Instead of bursting into violent ebullition, it 
lies in a shape like a flattened sphere, moving about — 
constantly, but not boiling. The cup is allowed to 
cool, the water keeping the spheroidal state, but 
losing heat slowly. After a while the cup gets so 
cool that the water can touch the metal, whichis still 
hot. Violent boiling begins and gets more and more 
violent, with a curious crescendo effect, until the water 
is reduced considerably in amount, when perhaps 
the small residue resumes the spheroidal condition 
for a few seconds more. 

An excellent cup for the experiment can be made 
by hollowing out a thickish disk of brass. A round- 
ended cylinder of wood may be placed vertically 
upon it, the brass resting over a hole somewhat 
smaller than itself, bored in a block of wood. A 
blow with a hammer on the wooden cylinder will 
cup the brass sufficiently to make it hold water. It 
may be heated over a candle or alcohol lamp, and 
the water may be poured in froma spoon. A silver 
coin makes a still better cup. A long wire handle 
with one end thrust into a cork and the other bent 
into a ring will answer to hold it. 

The demonstration, to show that the drop does 
not touch the metal, is illustrated in the cut. A drop 
of water rests on a Crookes layer over a hot flat 
silver plate. It may be projected by a magic lantern 


LIQUEFACTION OF GASES. 83 


on the screen or may be looked at directly. In 
either case it is seen that hght passes between drop 
and plate. 

The importance of the spheroidal state in relation 
to the liquefaction of gases cannot be overestimated. 
It alone has rendered possible the achievement of the 
extraordinary results of the last few years. Except 
for the spheroidal state, it would be a matter of the 
greatest difficulty to manipulate liquid gases, and 
the perils of liquid air would be beyond estimate. 


= —= 


Demonstration of Existence of Crookes Layer in 
Spheroidal State. 


But owing to the existence of the spheroidal state, 
and to its ready assumption by liquid gases, we are 
able to handle them much as we should water, 
although it is literally the same as if we kept water 
in red hot vessels. The experiments just described 
show how easy it is to do this. It is still easier to 
_keep liquid air in vessels at atmospheric temperatures 
because the atmospheric temperature keeps our 
vessels, in a sense, almost red hot for liquid air. 
They are maintained at the temperature producing 


84. LIQUID AIR AND THE 


the spheroidal state without the need of any artifi- 
cial source of heat. 

A familiar experiment in the solidification of gases. 
is the production of carbon dioxide snow. This 
intensely cold solid can be handled with impunity, 
it can be taken into the mouth, but does no harm, 
unless it is pressed against the skin, when it pro- 
duces a bad blister from the intense cold. It is pre- 
vented from touching the skin by a Crookes layer, 
although it is hard to believe that a Crookes layer 
could support a solid of fixed shape on its cushion, 
but such must be the case. The support of the drop 
of water is easy to comprehend, because the drop 
flattens down until it is of the same shape as the 
body it rests on, and, adapting itself to the shape, is 
practically at even distance from it as concerns its 
lower surface, so that all the molecules have practi- 
cally the same length of path. But to imagine an 
irregular lump of carbon dioxide snow so supported 
is not so easy, although we know that it occurs. 

Yet a common experience is that many intensely 
cold objects can be handled without hurting the 
skin, and in many cases it is due to the spheroidal 
state, or at least to the formation of a Crookes layer. 


LIQUEFACTION OF GASES. 85 


CELA P Dr he Lv 
PHYSICS AND CHEMISTRY OF AIR. 


The atmosphere as an ocean—What air is—Its constituents— 
Relations of air to living beings—The chemist’s and 
physicist’s view of air—lIts constancy of composition— 
Carbon dioxide—Oxygen—Nitrogen, argon and other 
constituents. 


The physics of the atmosphere is very simple. 
The members of the animal world are often said to 
walk about on the bottom of an ocean of air, like 
crustaceans in the ocean of water. As fish swim 
about in the water of the actual ocean, so may birds 
and flying insects be noted as tenants of the atmo- 
sphere itself. There are, however, very great and 
fundamental differences ; im analogy is a very in- 
complete one. 

The fish and crustaceans live surrounded by a 
medium whose specific gravity is not far different 
from their own. A fish not only swims in water, 
but floats init. By muscular contraction of his air 
bladder, he can increase his specific gravity so as to 
sink toward the bottom, or he can increase its size 
and rise toward the surface. Neither bird nor in- 
sect floats in equilibrium in the air. They are sus- 
tained by mechanical energy, derived partly from 
their own muscular system and partly, perhaps, by 
the internal energy of the air, due to variations in 
velocity of air currents. A crab has but the slightest 


£6 LIQUID AIR AND THE 


hold upon the bottom of the water over which he 
crawls. Almost all his weight is buoyed up by the 
water. When he crawls on the shore, his legs have 
probably over eight hundred times as much weight 
in the concrete to deal with as when he is in the 
water. | 3 

Thus, our atmosphere has a far different relation 
to us than is held by the true ocean of liquid matter 
that spreads over so large a proportion of the 
earth’s surface toits tenants. Its chemical constitu- 
tion also is fundamentally different. 

Water is a chemical compound, containing in 
chemical combination two elements, oxygen and 
hydrogen. The composition of its molecule is ex- 
pressed by saying that it contains two atoms of 
hydrogen and one of oxygen. If water is decom- 
posed, it resolves itself into two volumes of hydrogen 
to one volume of oxygen. A cubicinch of water 
will give about one and a half cubic feet of the gases 
named. | 

The atmosphere, the survivor of countless geolo- 
gic ages, left after terrestrial changes of every kind, 
which has been warmed by centuries of sunlight, 
and which has been the theater of electric disturb- 
ances of the most violent kind, and which has been 
acted on by the tremendous vegetation of the car- 
boniferous era, remains a simple mixture of gases, as 
far as its essential constituents are concerned. The 
constituents are not chemically combined, but are as 
free from any alliance with each other as the clay of 
the Mississippi and Missouri is from any fixed com- 
bination with the water that carries it in suspension 
toward the Gulf of Mexico. 


4 


LIQUEFACTION OF GASES. 87 


For many years the composition of air has been 
given in text books as approximately consisting of one 
volume of oxygen and four volumes of nitrogen. 
This has proved an error. A chance discovery that 
nitrogen prepared trom chemical sources had a dif- 
ferent specific gravity from that prepared from the 
atmosphere was brilliantly utilized by the discoverers, 
Lord Rayleigh and Prof. Ramsay. They were en- 
gaged in physical research, and having lighted upon 
this very extraordinary fact, explained it by the dis- 
covery that a third element, argon, exists in air. It 
was a contribution from physics to chemistry. A 
chemist would not have had the audacity from 
purely chemical considerations to believe or suggest 
that an undiscovered element lay hidden in our 
atmosphere, and that we had breathed an unidenti- 
fied gas, and had analyzed our air without finding it 
or suspecting its existence. The discovery was so 
revolutionary that it formed another step on the road 
to scientific credulity which we are traveling. 
Science has done so much that we are prepared to 
believe anything which may be attributed to her. 
Since 1894 other elements have been found in the 
air, and we find all our text books further invalidated 
in their descriptions of the very air we breathe. 

Air is not a chemical combination, because its con- 
stituents have so little affinity for each other, and 
nitrogen has long been cited as an element of gene- 
rally feeble affinities, and rather of the inert type. 
But it has to yield the palm to argon in this regard. 
The latter seems to be able to combine with nothing 
whatever. 

Physiologically, our active relations with the air 


88 LIQUID AIR AND THE 


concern only its oxygen, leaving aside impurities. 
We use the oxygen in our bodies to maintain life. 
The human system burns up the food it eats, and 
exerts energy of various kinds. The nitrogen and 
other elements act as diluents only. The animal sys- 
tem can do nothing with either of them. 

An infinitesiinal amount of nitrogen in chemical 
combination may have very grave effects. A frac- 
tion of a grain of strychnine, which has as an essen- 
tial constituent a very small fraction of a grain of 
nitrogen, will kill a man. Without the nitrogen it 
would no longer be strychnine, and would be innocu- 
ous; so that in the case of this poisonous alkaloid, we 
find a small fraction of a grain of nitrogen an essen- 
tial in a deadly composition. 

Yet, in the case of the air, because of its nitrogen 
being in the free state, we breathe in and out of our 
lungs tons and tons of nitrogen, and it has no effect 
upon us whatever. It is only a diluent of the oxy- 
gen which we live upon. 

A cubic foot of air weighs about 536 grains. It is 
generally taken as the basis of specific gravity of 
gases, which is a misfortune, because it is only a 
mixture, and has nothing essentially fixed in its com- 
position. Yet it is rather remarkable that air 
always contains exactly the same proportions of its 
important constituents, and, therefore, always has 
the same specific gravity. There is nothing com- 
parable to it in nature, if we regard it as what it 
essentially is—a fortuitous yet absolutely uniform 
and identical mixture of independent and uncom- 
bined gases. 

The physicist can speak of air differently from 


LIQUEFACTION OF GASES. 89 


the chemist. For the first named it is an almost 
perfect gas, and he can speak of it as a typical gas. 
The chemist cannot do this. To him it is a mixture 
of gases, and he cannot term air a gas. 

Air supports combustion and life, on account of 
the oxygen which it contains. If the quantity of 
the oxygen in a volume of air is increased, it will sup- 
- port combustion with much more vigor than in the 
ordinary state. This increase may be effected by 
adding oxygen or removing nitrogen, or mechanical 
pressure may do it. In either case combustion be- 
comes more intense. In constructing foundations 
under water or under the water-level in soil, the 
engineer uses an inverted case, like a gigantic box. 
From it water is excluded by air pumped in it at 
high pressure, which may rise to fifty pounds pres- 
sure to the squareinch. These structures are termed 
caissons, and in them where air is used, compressed 
up to three atmospheres excess of pressure, there is 
in one foot of the compressed air four times as much 
oxygen as under ordinary conditions. A piece of 
lighted paper, when blown out in such an atmosphere, 
will relight instantly. This mode of increasing the 
oxygen increases, also, the nitrogen. The com- 
bustion is not nearly as vivid as with artificially en- 
riched air. | 

One would suppose that some difference in the 
composition of air would be possible under the con- 
ditions prevailing onthe earth. Itis being constantly 
drawn upon by animal life. Animals, in breathing 
it, rob it of a portion of its oxygen, and add carbon 
dioxide gas to it; the plant world adds to its oxygen 
and removes its carbon dioxide. Yet. so constant 


gO LIQUID AIR AND THE 


are the mixing and disturbance to which it is 
exposed, that it proves the same when subjected to 
analysis, no matter where collected—practically the 
same, for there are slight variations which can be 
detected in the percentage of its impurities. 

The principal one of these last named substances 
is carbonic acid gas or carbon dioxide gas. By the 
rules of chemical terminology, this gas should be 
called carbonic oxide, but a concession to long usage 
is made in its case, and the older names are adhered 
to. It is a product of animal respiration, and is a 
chemical compound, each molecule containing one 
atom of carbon and two of oxygen. It is about fifty 
per cent. heavier than air, but, by the law of diffusion, 
tends to mix itself with perfect evenness with the 
lighter air. It is a product of all combustion, our 
chimneys delivering quantities of it. An ocean 
steamer pours out from her funnels nearly a ton a 
minute. Dissolved in water, it gives at aslight flavor, 
and is an antidote to flatness of taste of the fluid. It 
makes soda water and aerated beverages in general — 
sparkle and effervesce. It has played an important 
role in the: liquefaction of gases. It has itself been 
one of the earliest ones experimented on with any 
degree of success, and has been liquefied on the com- 
paratively large scale for many years. It has been 
a good object for experimenters to practice on in 
order to enable them to liquefy other gases which 
less readily succumb to pressure and cold. 

Its history is not without its tragic side. There 
are many caves and wells in which it accumulates. 
To enter and remain in one of these means a speedy 
death by asphyxiation. Casks or vats in breweries 


LIQUEFACTION OF GASES. or 


get filled with it in the fermentation process, and 
many instances of death to workmen, who incau- 
tiously descended into them, are told of. In its lique- 
faction at least one fatal explosion has occurred, as 
we shall see later. 

The liquid carbon dioxide possesses one very 
striking peculiarity. It cools so rapidly when re- 
leased from confinement that it renders latent so 
much heat as to produce large quantities of carbon 
dioxide snow. Other liquids solidify in part when 
allowed to evaporate rapidly, but none does it with 
such facility as carbon dioxide. 

When air is liquefied, a cloudy appearance is al- 
ways presented, which is removed by filtering it 
through filter paper. This cloudiness is attributed 
to solid carbon dioxide disseminated like pulverized 
chalk through the liquid. 


92 LIQUID AIR AND THE 


GHAP GEARS Ve 
THE ROYAL INSTITUTION OF ENGLAND. 


The Royal Institution—Its origin and objects—Count Rum- 
ford—Sir Humphry Davy—The Pneumatic Institute— 
Davy’s experiments in inhaling poisonous gases—His 
engagement as director of the Royal Institution—His 
views on the utility of liquefying gases. 


The Royal Institution of England has been iden- 
tified for more than three-quarters of a century with 
the liquefaction of gases. Davy, Faraday and Dewar 
have associated this line of research firmly with it. 
The recent investigations of Dewar and _ his associ- 
ates have been performed in part in the laboratory 
where Faraday worked so patiently with his bent 
tubes and did work which appears of such extra-_ 
ordinary merit, when his limited appliances are con- 
sidered. 

The Royal Institution was founded in 1799. In 
1796, Sir Thomas Bernard, the Rt. Rev. Shute Bar- 
rington, LL.D., William Wilberforce and Mr. Elliott 
founded the “ Society for Bettering the Condition of 
the Poor.” One of its principal objects was the 
establishment of an institution to teach the applica- 
tion of science to the advancement of the arts of 
life. 

A select committee was appointed in 1799 to con- 
fer with Count Rumford on the matter, subscriptions 


‘MOIJNyYsUy [eAOY oq} Jo Aroyer0qe’yT 


semznioyy 8,04p ep Jo fs N0Gy 


LIQUEFACTION OF GASES. 93 


were received, and the Royal Institution was estab- 
lished. 
Count Rumford, who took such an interest in its 


organization, was an American, Benjamin Thompson 
by name, born in 1753, in Woburn, Mass. His life 


04 LIQUIDVATRVAN DSi 


was a curious medley of diplomatic and army ser- 
vice and scientific study. He pretty thoroughly 
expatriated himself, his politics during the Ameri- 
can revolution being on the Tory or Royalist side. 


= 2S Anil W/ 
== Oly 
SS TT 
pT WINN 


+ 


Lecture Room at the Royal Institution. 


Courtesy of McClure’s Magazine. z 


Yet Harvard College and the American Academy 
of Sciences were remembered in his will. He 
married the widow of Lavoisier, the famous French 
chemist, whose almost prophetic words on the lique 


LIQUEFACTION OF GASES. 95 


faction of gases are proudly quoted by the French 
Academy of Sciences. 

From an official copy of the charter and by-laws 

of the Royal Institution of Great Britain, dated 
1835, we learn something of the early history of the 
foundation of the society. 
It was legally established under a charter dated 
1800, in the days of George the Third, and in 1810 
its powers and functions were eniarged and con- 
firmed by act of Parliament. It was a somewhat 
high priced society, as such things go. The entering 
member had to pay five guineas admission fee, and 
the annual dues were also five guineas. The enter- 
ing member had to pay five guineas in addition to 
the above, to be devoted to the library or to some of 
the collections. 

Mr. John Fuller was one of the great benefactors 
of the Institution. He established two professor- 
ships on foundations of 43,333 6s. 8d. each, which 
sums constitute two-thirds of 410,000, for which 
the Institution was his debtor. 

The Fullerian Professorship of Chemistry is the 
one of most interest in connection with our subject. 
Its first incumbent was Michael Faraday. The 
chair was established in 1833, ten years after Fara- 
day’s first work on the liquefaction of gases. Fara- 
day’s appointment in the same year is chronicled in 
the pamphlet of 1835, just alluded to. The donor 
did not long survive his f :undation of the chair. In 
the Philosophical Magazine for 1834, we find _re- 
corded a meeting of the Royal Institution, held on 
April 18 of that year, on account of the death of 
Mr. Fuller, who had done so much for the Institution. 


96 LIQUID AIR AND THE 


Prof. James Dewar now occupies this chair. 

Count Rumford had heard of the young scientist, 
Humphry Davy,and he engaged him a few years 
after the founding of the Institution, when only twenty- 
two years old, to be director. At first Count Rumford 
distrusted Davy and felt that he had been engaged 
precipitately. There were certain peculiarities about | 
him which caused him to produce an unpleasant im- 
pression. But it very soon transpired that Davy 
was a most capable chemist, although it was im- 
possible to foresee the renown he was destined to 
win for his country and for the Royal Institution. It 
is said that Count Rumford wished to find some one 
to give fame to the Institution. It soon appeared 
that he had made a most happy choice, and Davy 
gave it the most liberal meed of fame by his re- 
searches and discoveries. 

Humphry Davy was born in Penzance, Cornwall, 
Eng., December 17, 1778. He early in life showed 
a great fondness for science. A Dr. Beddoes had 
established at Clifton, near Bristol, a sort of hospital 
_ for the investigation of the treatment of disease by 
the application of gases in general. It was entitled 
the Pneumatic Institution. Davy was engaged to be 
the superintendent and accepted, although he was 
but nineteen years old. 

As we now look back upon Davy’s early engage- 
ment, it is impossible to avoid feeling that the scheme 
in which he was embarked savored of strong peculi- 
arity, to say no more. Yet he inspired it with rays 
from the lamp of true science, and thereby brought 
the genuineness of his character more strongly than 
ever to the front. 


LIQUEFACTION OF GASES. Q7 


He was engaged to test the action of gases as 
remedial agents. He came very near proving their 
efficacy as a means of bringing about the death of 
subjects submitted to them. This was in his own 
person. He experimented by personally inhaling a 
number of different gases, a class of experiments 
which showed, in the state of science as it existed at 
that early day, the most intrepid courage.- He 
experimented extensively with nitrous oxide or 
laughing gas. To test the combined effect of nitrous 
oxide and alcohol, he stupefied himself by drinking 
wine, and tried, as soon as he could collect himself, 
the effects of deep inhalations of nitrous oxide. 

What he called nitrous gas was then tried, with 
rather disastrous results. We know now that, whether 
it was the lower or higher oxide, the ultimate effect 
of its reaction with the moisture of the mouth and 
mucous membrane would be to produce nitric acid 
within the system. This is exactly what his de- 
scriptions of the effects suggest. He burned his 
tongue and palate with it, it affected his teeth, and 
inflamed the mucous membrane. Then, not satisfied 
with this most disagreeable and dangerous experi- 
ment, he essayed what hecalled carbureted hydrogen. 

This time he nearly died. He first, by expiration, 
got all the air possible out of his lungs and then in- 
haled what we know now to be a poison, or a mix- 
ture of poisons, as it probably contained carbon 
monoxide and carbon dioxide with hydrocarbons. 
The description of his sufferings and almost death 
is impressive, when read in the light of our present 
knowledge. 

He tried carbon dioxide, but here Nature asserted 


98 LIQUID AIR AND THE 


herself, and he could not get the pure gas into his | 
lungs. Not to be beaten by the spasmodic closing 
of the epiglottis, he diluted the gas with air and tried 
it that way. 

At twenty-two years of age we find him engaged 
by Count Rumford for the Royal Institution, inde- 
fatigably working in chemistry and physics, dis- 
covering the metals of the alkalis, producing the 
electric light, and after he had been but a few years 
in its service, doing one of the greatest services to 
science that ever fell to the lot of man to do—the 
engaging of Michael Faraday as his assistant in the 
Institution. 

It is said that Davy’s researches into the action of 
nitrous oxide or laughing gas on the human system 
were what led to his appointment to the Royal In- 
stitution. | 

Davy was very far-sighted in his views. He saw 
great possibilities in the liquefaction of gases. 
He said that it offered a way of impregnat- 
ing water with gas without mechanical means. 
Soda water has since his time been made thus. 

He said that great cold can be produced by 
liquid gases allowed to evaporate, and suggested 
the use of this faculty for preserving food. This 
outlines one of the cold storage processes, and it is 
hoped that liquid air may serve precisely the pur- 
pose outlined nearly eighty years ago by the great 
English philosopher. 

Davy also had a great faith in the possibilities of 
liquefied gases as agents for generation of power. 
One of his papers (Philosophical Transactions, vol. 
xxiii., page 199) is devoted to this topic, and he gives 


LIQUEFACTION OF GASES. 99 


figures to show what great power could be obtained 
from liquid carbon dioxide and the other gases 
which had been liquefied, and we find that, early in 
the life of the Royal Institution, Brunel tried the 
experiment of running an engine with liquefied 
carbon dioxide. 

In connection with the ‘subject of the liquefaction 
of gases, three names bring the Royal Institution 
prominently into notice: Davy, Faraday and Dewar. 
The first did comparatively little, but his sugges- 
tions were striking and suggestive. 

The Royal Institution has struggled along for 
abouta century, its centennial is at hand as this book 
goes to press, and the fine work done by Dewar and 
his associates in liquefying gases fitly marks the clos- 
ing years of its first century of existence. Faraday’s 
connection with it did more than was due merely to 
his far-reaching researches in chemistry and physics. 
The Institution has never been richly endowed, and 
for twenty-six years Faraday is said to have kept it 
alive by his lectures. He kept its accounts, and 
noted every expenditure down to the last farthing. 
The Institution gave him a fixed income of 4100, 

and eventually the Fullerian professorship, appoint- 
ing him for life, with the privilege of giving no 
lectures. The salary was then placed at £100. 

In the same year the Institution was in trouble, 
and a committee reported on salaries, advising that 
no reduction should be made in Faraday’s salary, 
“ £100 per annum, house, coals and candles,” which 
can only be taken as a compliment to the young 
scientist. 


ie 


LIQUEFACTION OF GASES. Io] 


CEEAP TER. Vi 
MICHAEL FARADAY. 


Michael Faraday—His early life—KEarly devotion to science— 
His introduction to Humphry Davy — Attendance -at 
scientific lectures—Engagement at the Royal Institution 
—Injuries from explosions in the laboratory—European 
tour with Davy—Rivalry of scientific men—Davy and 
Faraday as rivals—The liquefaction of chlorine—Davy’s 
share in the experiment—Davy’s opposition to Faraday’s 
election as fellow of the Royal Society—Dr. Paris and 
the liquefaction of chlorine—Faraday’s descriptions of 
his liquefactions — Explosions — Northmore’s priority 
published by Faraday——Notes on Faraday’s liquefaction of 
various gases—Exhibition of Thilorier’s apparatus—Later 
work in liquefying gases—Discovery of the magnetism of 
oxygen gas—His death—Bent tubes as used by Faraday 
— Experiments with use of bent tubes—The Davy-Fara- 
day laboratory. ) 


Michael Faraday was born on September 22, 1791, 
at Newington, Surrey, England. His family was 
poor, with no pretensions to being in any but a low 
social level as society is organized and differentiated 
in England. His mother, who Sived until 1838, was 
very proud of her son and his honors, although 
quite insufficiently educated to at all enter into his 
life’s work. She was an excellent and extremeiy 
neat housekeeper. Faraday’s education comprised 
little more than the rudiments of reading, writing 
and arithmetic. In 1804 he went as an errand boy to 


102 LIQUID AIR AND THE 


a bookseller, George Ribeau. Part of his work was 
the delivery of newspapers. Each copy circulated 
among a number of readers, for Ribeau dent the 
papers instead of selling them, and Faraday had to 
circulate in succession from house to house with 
the same copies. 

In 1805 he began his apprenticeship as book- 
binder and stationer, and at once began reading 
everything scientific that came in hisway. He made 
simple experiments in chemistry, built an electric 
machine and other apparatus, and began to attend 
scientific lectures. In 1812 he heard four lectures 
by Sir Humphry Davy, andthe same year he took 
an engagement as a journeyman bookbinder. The 
position was very disagreeable to him. 

Before he had completed his seven years apprentice- 
ship he took the step which shaped his whole life. 
He wrote to Sir Humphry Davy, asking for a posi- 
tion and sending elaborate notes of Davy’s lectures 
which he had taken. He received a reply which he 
termed “immediate, kind and favorable,” and early 
in March, 1813, he was engaged as assistant in the 
laboratory of the Royal Institution. 

The histories of the early years of great men’s 
lives are often of interest, and few exceed in this re- 
gard those of Faraday. Books were not so plentiful 
then as now, and Faraday used the opportunities 
which his trade of bookbinder and stationer put in 
his way to read scientific works. A series of letters 
by him written to his great friend Abbott show the 
tendency of his thoughts to chemistry, and incident- 
ally show how indefinite were the theories on which 
the chemistry of that time was based; but Faraday’s 


LIQUEFACTION OF GASES. 103 


observations are often far in advance of the age. 
He speaks of the odor given off by metals when 
rubbed. Exactly this subject of odors, a very myste- 
rious one, too, has been the topic of recent investi- 
gation. He objects to the names muriate of sodium 
and chlorate of sodium for common salt, and savs 
that it should be called chloride of sodium, and 
sodium chloride is its name to-day. Another 
tendency of his mind was toward electricity. He 
gives the account of his making batteries, on the 
now old fashioned ‘“pile’’ system, placing disks of 
zinc and copper, one upon the other, with paper 
moistened with acid between the alternate pairs. 
With these he decomposed water and acids and tells 
the results in the letters which have bcen preserved. 

These letters, many of them written when he was 
but twenty years old, are wonderful examples of 
his intellectual powers. Here was a bookbinder’s 
apprentice, but twenty years old, self-educated, 
speculating on subjects which constituted the most 
recondite branches of science and speculating rightly. 
The instances given above are buta few out of many 
which could be cited to show the precocity of his 
genius. 

He kept a note book in which he entered the 
names and abstracts of articles in books and journals 
which had interested him. Sir Humphry Davy 
appears in it, for in this note book is the entry : 

“Galvanism.—Mr. Davy has announced to the 
Royal Society a great discovery in chemistry—the 
fixed alkalis have been decomposed by the galvanic 
battery.” This he credits to the Chemical Observer. 

The greatest achievement of Sir Humphry Davy’s 


2OA. LIQUID AIR AND THE 


long career is noted by the humble apprentice, who 
was destined to succeed the older master and to 
equal or exceed him in renown. 

An interesting illustration of Faraday’s thorough- 
ness occurred when he was but nineteen years old. 
He had attended some lectures given by Mr. Tatum 
on natural philosophy. They were given at his 
residence, 53 Dorset Street, Fleet Street. To enable 
him to do justice to the illustration of these lectures 
he actually learned perspective, doing all the draw- 
ings in a quarto treatise on this subject. 

In this early work we recognize a threefold bent 
of his mind, always discernible in his long life’s work. 
Chemistry was the branch of science which first claim- 
ed his attention and electricity was the work which he 
took up later in life. Chemistry and electricity, it will 
be remembered, were the two principal studies of his 
youthful days. The third subject which interested 
him was lecturing, and early in lfe we find him a 
lecturer in the Royal Institution, and for year after 
year he lectured there, and held a higher position 
than perhaps has ever been awarded an English speak- 
ing scientific lecturer. He also wrote upon the sub- 
ject of lecturing and on the methods which should be 
followed in addressing audiences. He comes to the 
same conclusion which has so often been reached 
since—that a popular lecture will not be a good 
scientific one and that the converse also holds. From 
passages often quite long which refer to lecturing, 
the conclusion is drawn that he gave a great deal of 
thought to the subject and desired to achieve success 
in it. : 

On March 1, 1813, Faraday was engaged as assist- 


LIQUEFACTION OF GASES. TO5 


ant at the Royal Institution, at the salary of 25 
shillings a week and the use of two living rooms 
at the top of the building. At once he began his 
initiation into serious work by assisting Davy in in- 
vestigations into the properties of chloride of nitro- 
gen, one of the worst explosives known to man. 
He chronicles explosion after explosion with it, his 
hand is torn open, his eyelid is cut; Sir H., as he 
calls Davy, has his hand bruised. They ¢ry to 
distill it, and it explodes, and Davy gets the worst of 
it, his face being cut in several places. They know 
the danger they are in, and wear glass masks, and 
Faraday at last says that ‘‘ It is, as I before said, im- 
proper to consider it at any time as secure.” 

The dangers of science are appropriate to our 
subject. The liquefaction and compression of gases 
have given rise to many explosions, and to one of the 
worst explosions that has ever happened to an ex- 
perimenter. We shall see later how Faraday and 
others suffered in experiments in these fields. 

On October 13 of the same year, Sir Humphry 
Davy started on a tour over the Continent, on which 
Faraday was to accompany him. At the last moment 
Davy’s valet refused to go, and Faraday agreed to do 
certain things which more properly would have 
fallen to the lot of that functionary. This arrange- 
ment, it was understood, was only to last until Paris 
was reached. In reality Davy completed the tour 
without any valet, and Faraday shrewdly concluded 
_ that finally he preferred to do without one. 

In the early days of science there was a much 
greater spirit of rivalry among scientific men than at 
the present time. Seventy or eighty years ago there 


106 LIQUID AIRGAND IEE 


was a comparatively small body of scientific facts in 
the possession of man. The initial steps toward the 
acquirement of this knowledge had been made, and 
the acquirement and recording of facts proceeded 
more and more rapidly every year, until at present — 
we have been presented with amazing developments; 
one after another, which in their rapid succession 
have almost robbed us of the capability of being 
surprised. ; 

In reading the quaint story of the life of the book- 
binder’s apprentice Faraday, and of his experiences 
with Sir Humphry Davy during their continental 
tour, it is easy to perceive a sort of overriding ten- 
dency on the part of the older philosopher whose 
assistant he was. Faraday, too, had something to 
complain of from Lady Davy, but he seems to have 
held his own with her. Faraday’s complaint was 
that he was requested to do certain things on the 
tour which he had not urdertaken to do and against 
doing which he protested. At intervals after this 
journey, which took place in 1813-14, while he was — 
twenty-two and twenty-three years old, some notes 
of discord can be heard, and the culmination seems 
to have been definitely reached in 1823. We have 
little to do with the unpleasantness between Faraday 
and Sir Humphry Davy; so we may briefly dispose 
of it now. 

In 1823 Faraday did his first work on the lique- 
faction of gases. He liquefied chlorine and published 
the result, eventually disclaiming priority in favor 
of another investigator, Northmore, whose work is 
recorded later in this book. 

On May 1, 1823, he was proposed tor a fellow of 


LIQUEFACTION OF GASES. 107 


the Royal Society, of which Sir Humphry Davy was 
president. Faraday had succeeded by following 
Davy’s suggestions in liquefying chlorine. Davy 
had not told him that liquefaction of chlorine was to 
be anticipated in carrying out his suggestions, and it 
was liquefied and identified as chlorine in Davy’s 
absence. The work was therefore Faraday’s own. 
Yet Sir Humphry Davy seems to have been jealous 
that part of the credit should attach to his junior 
associate. At any rate, it is definitely certain that 
Davy opposed Faraday’s election asa fellow of the 
Royal Society, and actually asked him to withdraw 
the paper of nomination. Faraday said that, as the 
paper had been posted by his proposers, he could not 
take it down, and, on a further request, said that he 
knew that his proposers would not take it down. 
Then Davy said that he, as president, would take it 
down. 

One of Faraday’s proposers afterward told him 
that Davy spent an hour arguing that Faraday 
should not be elected. The certificate of his pro- 
posers had to be read at ten meetings. On the final 
ballot there was only one black ball. It is to be 
hoped that it was not thrown in by Sir Humphry 
Davy. After this Faraday and Davy got on more 
smoothly in all their relations. The culmination of 
their troubles seemed to mark the end of disturb- 
ance. 

Thus Faraday’s connection with the liquefaction of 
- gases is concerned with one of the more important 
episodes of his life. 

A gossipy life of Sir Humphry Davy has been 
_written by Dr. John Ayrton Paris, who was an 


108 : LIQUID ‘AIR AND HE 


intimate fend of the philosopher, and who seems to 
have had‘a fancy for natural science. He was the 
first person to witness the liquefaction of chlorine by 
Faraday. The passage from his life of Davy in 
which he describes it is well worth transcribing, if — 
only for the picture it gives us of the scientific life of 
those days. Dr. Paris had been invited to dinner 
with Sir Humphry Davy to meet the Rev. Uriah 
Tonkin. Sir Humphry had just set Faraday to 
work heating chlorine hydrate in a closed tube. 
We can see in our minds the brilliant company 
assembled at Sir Humphry’s for dinner, while, not 
far away, Faraday, alone in the laboratory, was 
heating his chemical in a sealed tube, in imminent 
danger of blowing his eyes out. We can see Davy’s 
biographer, dressed for dinner, standing by the side 
of the ex-bookbinder in his laboratory garb, watch- 
ing and commenting on the operations of the master- 
hand. We can do no better than let Paris himself 
tell the story of Faraday’s liquefaction of the gas 
chlorine: 

“T had been invited to dine with Sir Humphry 
Davy on Wednesday, the 5th of March, 1823, for the 
purpose of meeting the Rev. Uriah Tonkin, the heir 
of his early friend and benefactor of that name. On 
quitting my house for that purpose, I perceived that 
I had time to spare, and I accordingly called on my 
way at the Royal Institution. Upon descending 
into the laboratory, I found Mr. Faraday engaged in 
experiments on chlorine and its hydrate in closed 
tubes. It appeared to me that the tube in which he 
was operating upon this substance contained some 
oily matter, and I rallied him upon the carelessness 


LIQUEFACTION OF GASES. 109 


of employing soiled vessels. Mr. Faraday, upon in- 
specting the tube, acknowledged the justice of my 
remark, and expressed his surprise at the circum- 
stance; in consequence of which he immediately 
proceeded to: file off the sealed end, when, to our 
great astonishment, the contents suddenly exploded 
and the oily matter vanished. 

“Mr. Faraday was completely at a loss to explain 
the occurrence, and proceeded to repeat the experi- 
ment with a view to its elucidation. I was unable, 
however, to remain and witness the result. 

‘‘Upon mentioning the circumstance to Sir Hum- 
phry Davy after dinner, he appeared much sur- 
prised; and, after a few moments of apparent ab- 
straction, he said, ‘I shall inquire about this experi- 
ment to-morrow.’ 

“Early on the next morning I received from Mr. 
' Faraday the following laconic note: 


“DEAR SIR: The oc/ you noticed yesterday turns 
out to be liquid chlorine. . 
“¢ Yours faithfully, 
“ «MICHAEL FARADAY.’ ” 


it is seldom that we find such an interesting side- 
light thrown upon the pages of early scientific his- 
tory. It is a contribution to the everyday life of the 
old London world for which we cannot be too grate- 
ful to Dr. Paris. It reads like a bit out of Pepys’ 
Diary. The unprejudiced reader of the present day 
will envy Dr. Paris his interview with Faraday, and 
few will feel that the meeting with the Rev. Uriah 
Tonkin should excite the same feeling to as great a 
degree. 


I1o LIQUID AIR AND THE 


In Faraday’s letters we find several references to 
his work on the liquefaction of gases. In 1823 he 
had received from Davy the suggestion mentioned 
above to heat hydrate of chlorine in a sealed glass 
tube. This he did, and the fluid separated into two 
layers, and Faraday identified the lower layer as 
true liquid chlorine. He, to confirm this, com- 
pressed some chlorine gas in a tube, sealed it, cooled 
it, and again obtained liquid chlorine. The latter 
gas was dried before compression, so as to make the 
experiment absolutely conclusive. 

He was troubled by. his tubes bursting. His eyes 
were once burnt, another time were cut. He speaks 
of them as being filled with broken glass, the explo- 
sion being so violent as to drive pieces of glass 
through the window panes, “like pistol-shot,”’ he 
writes. 

This was in 1823. He found, on investigation, 
that neither he nor Sir Humphry Davy had priority 
in condensing gases into liquids, and so he published 
the article spoken of elsewhere (pagerr8) telling of 
Northmore’s work. 

In a letter written in 1836 he refers to Monge and 
Clouet’s liquefaction of sulphur dioxide probably 
before 1800. This gas Faraday prepared by treat- 
ing mercury with concentrated sulphuric acid, and 
found no difficulty in liquefying it. He attached 
credence to Monge and Clouet’s very doubtful rec- 
ord, because he found the liquefaction of sulphurous 
oxide such an easy experiment to perform. 

Sulphureted hydrogen he made in a sealed tube 
by first pouring into it some hydrochloric acid. 
Over this he placed a piece of platinum foil, and on 


LIQUEFACTION OF GASES. III 


this placed iron sulphide. ‘The tube was then sealed, 
the acid was brought into contact with the sulphide 
of iron, and the tube was left for some days for the 
acid to act upon the sulphide. If necessary, the 
filled end of the tube was heated while the other end 
was cooled. He obtained a very limpid, clear fluid, 
whose specific gravity he puts at about ogo. 

When he came to experiment with carbon dioxide 
gas, he was badly troubled by explosions. He pre- 
pared it from ammonium carbonate and _ concen- 
trated sulphuric acid. He credits it with requiring 
360 atmospheres at o° C. (32° F.) for liquefaction. 

Euchlorine, as it was then called, he made by 
acting on potassium chlorate with sulphuric acid. 
After twenty-four hours’ standing he heated the mix- 
ture to nearly 38° C. (100° F.), cooling the other end 
of the tube to —16° C. (3° F.) and condensing a dark 
yellow fluid. 

Nitrous oxide or laughing gas was prepared by 
heating ammonium nitrate. This he heated first to 
partial decomposition, in order to get it as drv as 
possible. The procedure was rather superfluous, as 
in the decomposition water is inevitably produced, 
no matter how dry the salt is. Again he was 
troubled with explosions, for he got the pressure up 
to 50 atmospheres at 7°2° C. (45° F.) | 

Cyanogen he produced by heating dry mercury 
cyanide in one end of the sealed tube, and the cya- 
nogen was condensed as a liquid in the other end. 

Ammoniacal gas was absorbed by silver chloride. 
He found that too grains of silver chloride would 
absorb 130 cubic inches of the gas. This highly 
charged salt of silver, heated in the sealed tube, 


I12 LIQUID AIR AND THE 


evolved ammonia in abundance, and he liquefied it 
without trouble. 

Hydrochloric acid was made from ammonium 
chloride and sulphuric acid, and liquefied. 

This was the work done in 1823. In another place 
will be found a full description of the bent tubes 
used by Faraday to liquefy gases. These tubes are 
still useful in demonstrations and for tests on the 
small scale, although their use is not free from 
danger. 

It is reported by Prof. James Dewar, of the Royal 
Institution, that it appears from old papers or 
records that in 1838 Faraday exhibited at the Royal 
Institution Thilorier’s apparatus for the liquefaction 
of carbon dioxide, lent him by Mr. Graham. This 
was a few years only after its firs: construction by 
the French scientist. The date of the lecture in 
which it was exhibited by Faraday was May 18, 
1838. The exact date is recorded in the Philosophical 
Magazine, vol. xii., 1838, page 536. 

With the exception of this incident, we have to 
pass over a long period, some twenty-odd years, 
before we find Faraday again seriously occupied 
with the liquefaction of gases. When past his fiftieth 
year he returned to the subject. He had then done 
much of his life’s work, he had formulated theories 
of electricity, especially in relation to magnetism, 
and was in the midst of the electric studies of his 
life, which lasted until 1855. His work in electricity 
underlies all the amazing developments of the last 
two decades, and the action of the magnetic circuit 
and the production of definite voltages from dynamo- 
electric generators were never brought to an intelli- 


LIQUEFACTION OF GASES. I13 


gible condition except by the use of lines of force, 
and these were a device of Faraday’s, which enabled 
him to picture in his mind the action of a magnetic 
field of force upon a conductor swept through it. 

To return to the liquefaction of gases, it was in 
1845 that he began anew to try to liquefy various 
gases, and the results are embodied in a paper pre- 
sented to the Royal Society and published in ab- 
stract in the Abstracts of the Papers communicated 
to the Royal Society of London under date of 
January 16, 1845. Some additional remarks on the 
same subject are given in the same volume under 
date of February 20. 

He combined mechanical compression with cool- 
ing, using two air pumps, working in succession, one 
after the other, reminding us of Pictet’s pumps, de- 
scribed on page 165. The first one had a cylinder one 
inch in diameter. The next pump, whose cylinder 
was one-half inch in diameter, took the compressed 
gas from the first one and gave a second com- 
pression. The gases were pumped into green 
bottle-glass tubes, one-sixth to one-quarter inch in 
external diameter. This seems a very small tube to 
employ, but the diameter is so stated in the abstract. 
The tubes were sealed at the upper end, which was, 
in some cases, bent downward so that it could be in- 
serted into a cooling mixture. The pressure could 
be raised to fifty atmospheres. He sometimes used 
tubes closed with brass stopcocks. 

The cold was produced by what he calls Thilorier’s 
mixture of solid carbon dioxide and ether. This 
gave a temperature directly of —76:7° C. (—106° F.) 
To increase the. cold he placed the mixture under an 


114 LIQUID AIR AND THE 


air pump and exhausted down to one twenty-sixth of 
an atmosphere. This gave him a temperature of 
—110° C. (—166° F.) His bath of carbon dioxide 
and ether, under these conditions, lasted only fifteen 
minutes. 

He found that several gases condensed to liquids 
at the atmospheric temperature under this degree of 
refrigeration. Sometimes he preserved them by 
sealing up the tubes, and they remained liquid at 
ordinary temperatures. Others troubled him by 
their chemical action on the cement employed in 
connecting his apparatus. Some he succeeded in so- 
lidifying. These were sulphur dioxide, sulphureted 
hydrogen, nitrous oxide, hydriodic acid, hydro- 
bromic acid and ammoniacal gas. He suggests the 
great availability of liquid nitrous oxide as a refrig- 
erating agent. 

It is interesting to note that he tried hydrogen 
and oxygen at 27 atmospheres, and failed to liquefy 
them. He also failed with nitrogen and nitric oxide 
at 50 atmospheres, carbon monoxide at 40 atmo- 
spheres, and coal gas at 32 atmospheres. 7 

His work was greatly facilitated by the adoption 
of low temperatures. In his use of a volatile freez-. 
ing mixture in a vacuum combined with mechanical 
pressure applied to the gas, we recognize the ele- 
ments of the work of most of his successors in the 
work of liquefying gases. 

Faraday did some of the greatest work of his life 
in the realm of electricity, and here we have to 
chronicle a discovery which is the basis of some 
very striking liquid air experiments. He found that — 
not only iron and a few other metals are attracted by 


LIQUEFACTION OF GASES. Ils 


the magnet, but he found that the gas oxygen is 
highly magnetic, the discovery of this fact coming 
after Baucalari’s discovery of the same. Baucalari 
was professor at Genoa. Faraday’s date was 1847. 

What strange exultation would have possessed his 
soul could he have seen liquid oxygen adhering in 
quantity to the pole-pieces of a magnet, and lying in 
a vessel over its poles and drawn by the attraction 
as if it were a veritable metal, although it is as far 
removed chemically from the metals as possible. 

After a long life, one of the most touching and in- 
teresting in the history of science, Faraday felt his 
powers gradually failing. . His life had few episodes 
outside of his scientific discoveries. Sir Humphry 
Davy, at last, did him justice; the disagreeable in- 
cident of 1823 was the last of its kind. 

At the age of seventy-five, on August 25, 1867, he 
died. He had spent all his scientific life in the 
Royal Institution, and left it as a veritable legacy 
the story of his work on the liquefaction of gases, so 
ably prosecuted in the same building by Prof. Dewar. 

Davy and Faraday are now commemorated by the 
Davy-Faraday Research Laboratory, in connection 
with the Royal Institution, founded by Dr. Ludwig 
Mond, which was opened in 1896. 


116 LIQUID AIR AND THE 


CHAPTER VII. 
EARLY EXPERIMENTERS AND THEIR METHODS. 


Perkins’ claim to have liquefied air—Its absurdity.-—North- 
more’s liquefaction of chlorine—Rumford’s experiments 
as commented on by Faraday—Babbage’s experiment ina 
drill holein limestone rock—Monge and Clouet’s alleged 
liquefaction of sulphurous oxide—Faraday’s liquefaction 
of chlorine—Stromeyer’s liquefaction of arseniureted 
hydrogen—Faraday’s bent tubes for liquefaction of gases 
— Manometer for use with them—Experiment in a straight 
sealed tube in the liquefaction of chlorine—-Davy’s sug- 
gested method—Cagniard de la Tour—His bent tube 
experiments—D. Colladon—His apparatus as still pre- 
served—Thilorier—His discovery of solid carbon dioxide 
—A fatal explosion—The improved Thilorier apparatus— 
Johann Natterer’s apparatus—His experiments—Loir and 
Drion’s solidification of carbon dioxide—Thomas An- 
drews, of Belfast. 


The first hint of the liquefaction of air is given in 
the Annals of Philosophy, new series, vol. vi., page 66, 
1823. It is merely a short note giving the title of a 
paper by Mr. Perkins. The paper was to be read at 
a meeting of the Royal Society, in 1823, but it was 
mislaid, and the Royal Society were spared the 
reading of it. 

Mr. Perkins says that he exposed air to a pressure 
as high as 1,1co atmospheres, which is nearly eight 
tons to the square inch, or over half the pressure 
produced in a modern cannon. He says that the air 


LIQUEFACTION OF GASES. Li7 


upon compression disappeared, and left in its place 
a small quantity of liquid, permanent when the pres- 
sure was removed, tasteless, and without action on 
the skin. Faraday says (Quarterly Journal, xvi., 
page 240) “it resembled water,” but thinks that it 
may be some unknown product of compressed air. 

The present generation, to whom liquid air in 
quantity has become a plaything, recognize in Mr. 
Perkins’ work a very simple state of things. Theair 
disappeared because it all leaked out, and the water 
vapor present was condensed by the high pressure 
and was left in the apparatus. Had Faraday been 
given a sample of Perkins’ “liquid air,’’ he would at 
once have identified it as water. 

In 1805 and 1806 papers by Thomas Northmore 
appeared in WVicholson’s Journal, xil., page 368; xiii., 
_ page 233. Northmore was experimenting to see what 
effect pressure had upon a mixture of gases. He 
had a compression pump, mercury gauge and re- 
ceivers, and pumped his gases directly into the re- 
-ceivers. He tried a metal receiver, but found it 
unsatisfactory and adopted a glass one. 

Very fine illustrations of some oi his screw con- 
nections, of his valve and of his siphon gauge, are 
given in the Journal. They show so little and such 
unimportant parts that it is rather surprising why 
such care was taken in so beautifully reproducing 
them. 

He had all sorts of difficulties. His stopcocks 
troubled him, as they leaked. The metal parts of 
his pump corroded under the effect of the gases he 
experimented with, and his receivers exploded 
several times. 


118 LIQUID AIR AND THE 


He condensed chlorine gas, then called oxy- 
genated muriatic acid, describing the experiment as 
follows: 

‘“ Upon the compression of nearly two pints of oxy- 
genated muriatic acid in a receiver two and a quarter 
cubic inches capacity, it speedily became converted 
into a yellow fuzd.”’ 

He then comments upon its pungent odor and its 
great volatility. 

He thinks that he liquefied sulphurous acid, but 
his pump piston became immovable very soon, On ac- 
count of the action of the gas. He says that he ob- 
tained ‘a thick slimy fluid, of a dark yellow color.” 
This, he claims, confirms Monge and Clouet’s ex- 
periment, as given in Accum’s “Chemistry,” vol. i., 
page 319. 

Faraday, whose mind was pre-eminently illumined 
and guided by the lamp of truth, contributed 
to the Quarterly Journal of Science, Literature and 
the Arts, vol. Xvi., page 229 ef ‘seg., a -papereon 
the history of the condensation of gases. He 
states that when he liquefied chlorine gas a 
little earlier in the year 1823, he was unaware 
that “any of the class of bodies called gases had been 
reduced to the fluid form.” He started an investi- 
gation into the history of the subject. He found 
that Count Rumford, in 1797, had exploded gun- 
powder in closed vessels and had claimed to confine 
the gases produced within the space previously oc- 
cupied by the powder. This may, with all due re- 
spect to the distinguished inventor, be doubted. 
Faraday speaks of the hissing sound observed when 
the products of combustion in Rumford’s experi- 


LIQUEFACTION OF GASES. 18 fe) 


ment were allowed to escape, and concludes that 
this may have been due to liquefied carbon dioxide. 

The accepting a hissing sound as proof of liquefac- 
tion reminds us of Pictet’s claim for the liquefaction 
and solidification of hydrogen, when so much was 
inferred from the noise due to the escaping of the 
stream and to its impinging on the floor. 

Faraday does not make any point of the fact 
that carbon dioxide snow or solid carbon dioxide 
should have been produced. That this is formed 
when the liquid in question is permitted to evapor- 
ate under atmospheric pressure was unknown at the 
time the paper was written. 

A most curious experiment on the decomposition 
of marble under pressure was made by Mr. Babbage 
in 1813. He wished to ascertain whether pressure 
would prevent chemical decomposition. The idea, 
in our days of high grade explosives, and when the 
recent explosions of liquid acetylene have done so 
much to bring a safe illuminant into evil repute, 
seems curious. But Mr. Babbage, with his inquiring 
mind, had a hole thirty inches deep and two inches 
wide drilled in the limestone rock at Chudley Rocks, 
Devonshire. A quantity of strong hydrochloric 
acid was poured into the hole, and a conical wooden 
plug, previously soaked in tailow, was driven into 
the mouth of the hole and the experimenters stood 
off and waited. They might be waiting yet, as far 
as the experiment went, for nothing occurred, the 
rock was not split and the plug was not expelled. 
Faraday thinks that liquid carbon dioxide may have 
been formed and lain quietly in the hole. He over- 
locks an important point—that the water of the 


120 LIQUID AIR AND THE 


hydrochloric acid would assist in lowering the 
pressure by its solvent action on the carbon dioxide. 
Mr. Babbage’s conclusions are not given. 

Faraday, in his paper on the history of the lque- 
faction of gases, says it is asserted that sulphurous 
acid gas had been liquefied by Monge and Clouet, 
but that he had not succeeded in finding any account 
of their process. Their work dates back to the end 
of the eighteenth century. Anyone who wishes to 
investigate the subject will find it clouded by un- 
certainty. On page 234 of the Quarterly Journal 
of Setence, Literature and the Arts, vol. xvi. 
will be found references to seven authorities, and 
there seems to be no certainty obtainable from any 
of them. Faraday reaches the conclusion that the 
degrees of pressure and of cold required to liquefy 
sulphurous oxide are so slight that there is little 
doubt that Monge and Clouet did actually accomplish 
the experiment. The original authority cited for 
their work is Fourcroy, vol. ii., page 74. He states 
that the gas is liquefiable at ‘28° of cold.” This tem- 
perature refers probably to the Centigrade scale, 
and reduces to —18°4° F. 

The early experimenters had found that by expos- 
ing chlorine gas, produced by the usual ‘methods, to 
cold, a solid substance was produced which was sup- 
posed to be solid chlorine. About 1810 this was 
examined by Sir Humphry Davy, who found it to 
be a compound of water and chlorine. Faraday 
analyzed it, and found it to contain approximately 
‘27-7 chlorine, 72°3 water, or 1 proportional of chlo- 
rine and 10 of water.” | 

Modern analysis but-slightly changes Faraday’s 


LIQUEFACTION OF GASES. 121 


figures, to chlorine 28 per cent., water.72 per cent., 
giving as a formula CLOH;. The old investigators 
had not produced dry chlorine, and the substance 
which they cooled contained so much water that 
chlorine hydrate was produced by the refrigeration. 

Sir Humphry Davy suggested that exposing the 
chlorine hydrate to heat under pressure would prob- 
ably lead to some interesting results. 

Without detailing Faraday’s exact words, it may 
be enough to refer the reader to the Philosophical 
Transactions of the Royal Soctety of London, 1823, vol. 
xlll., page 160 e¢ seg.—a most sumptuous publication 
wherein the work is described in full detail by Fara- 
day. A subsequent note by Davy says that he 
thought one of three things might result from the 
experiment, and among them was the liquefaction of 
chlorine. 

This was the origin of the last and most bitter dis- 
pute between Faraday and Davy. More is said of it 
on pages 106and 107. After this the two lived on ex- 
cellent terms. It must also be said that it was a very 
one-sided dispute, as far as any acrimony was con- 
cerned, Faraday showing not the least spirit of con- 
tention. 

The assertion by Davy of what ideas were present 
in his mind when he suggested the experiment to 
his assistant was calculated to deprive Faraday of the 
entire glory of being the first to successfully liquefy 
chlorine. But the historical investigations of Fara- 
day showed him that nearly twenty years earlier 
Northmore had made liquid chlorine, so that the 
bone of contention was pretty well disposed of. 

Other less important liquefactions are that of 


122 LIQUID AIR AND THE 


arseniureted hydrogen, claimed for Prof. Stromeyer, 
of Gottingen, in 1805, but very much doubted by 
Faraday (Quarterly Journal, xvi., page 236) ; and that 
of hydrochloric acid, claimed for Mr. Northmore, in 
1805 (ibid., page 236; Mcholson’s Journal, xii., page 
368, Klli., page 232). 

The arseniureted hydrogen experiment, however, 
has a great subjective interest, as it illustrates the 
danger inherent in the work o1 the early chemists, 
This gas is so frightfully poisonous that its dis- 
coverer is said to have been killed by inhaling a 
single bubble. Yet we read of Stromeyer producing 
itin quantity, by digesting an alloy of 15 parts tin 
and 1 of arsenic in strong muriatic acid, collecting 
it over the pueumatic trough, and exposing it to the 
temperature pede by mixing snow and calcium 
chloride, in which, as a test of its coldness, several 
pounds or quicksilver had been frozen in the course 
o1 afew minutes. This was certainly a most-power- 
ful freezing mixture. Yet Faraday doubtsif the gas 
was really liquefied, as he himself had tried it at nearly 
—18° C. (o° F.) at a pressure of three atmospheres. 

Had any accident happened during these experi- 
- ments, had aretort burst or the high pressure ap- 
paratus exploded, the intrepid experimenters would 
have had a narrow escape with their lives, if they 
had not instantly succumbed to the poisonous gas. 

As for hydrochloric acid gas, whose liquefaction 
had been claimed by Northmore in 1805, Faraday 
concludes that as 40 atmospheres pressure are re- 
quired to liquefy it at an ordinary temperature, and 
as Northmore employed no cooling mixture, the 
supposed condensation did not take place. 


LIQUEFACTION OF GASES. 123 


For liquefying gases on the small scale when they 
can be evolved by heat, and at not too high pressures, 
the bent glass tubes devised by Faraday for this use 
may be employed. There are many.shapes given by 
him, two of which are more directly in the line of 
our subject. One is applicable where no liquid is 
given off in the process of producing the gas, for it 
must be produced in the tube. Another is used 
where some liquid, such as water, is evolved during 
the gas evolution process. 

The. simple bent tube is shown inthe cut. The 

tube as made is sealed at one end and bent in the 
middle. The gas-evolving material is placed in the 
closed end, and the other end, which has been left open 
for the introduction of 
the material, is closed 
after the introduction 
by melting the glass 5 
with a blow-pipe or  Faraday’s Simple Bent Tube. 
Bunsen burner flame. 
In the construction of the tube care must be taken 
to maintain a good thickness of the glass where it is 
drawn out for closing. Often in drawing a tube 
down the glass becomes too thin for strength. - 

If the gas is one which liquefies by pressure alone, 
all that is necessary is to hold the tube in the 
position shown and heat the full end. As the gas is 
evolved it produces pressure in the tube, and if the 
_ pressure becomes great enough, and if the tempera- 
ture of the empty end of the tube is cool enough, it 
liquefies and collects there in the liquid state. 

But often cold is required in addition to pressure, 
and this is secured by inserting the empty end of the 


124 LIQUID AIR AND THE 


tube into a freezing mixture. . Powdered ice and salt 
or powdered ice and calcium chloride are typical 
mixtures. 

The other shape of tube is shown in the next cut. 
The tube was held inverted, as shown in the upper 
figure, and the substances were inserted, as shown, 
into one or both bends, 6 andc. A long-stemmed fun- 
nel was used to pour the liquids through, if liquids 
were used. The ends, a and d, were then sealed, 
and, by turning the tube over, everything collected 

in one end, a. The tube was placed 
o with the empty end, d, in a freezing 

mixture. The end, a, was heated, 

if necessary. The liquefied gas 
, collected in the further end, and 
aly ° \ any liquid that distilled over was 
caught in the intermediate bend. 

To determine the pressure pro- 
duced in the tube, a small tube 
i closed at one end, o, and with a 
| short bit of mercury, z, in its bore, 
was placed in the experimental 
tube before closing it. As the pres- 

renee os aiming oni, foe: the mercury was forced 

Tahessand toward the end of the small tube 
Manometer. containing it. This it did because 
the air confined between the mer- 
cury and the ae of the tube is compressed. If the 
distance from the mercury to the closed end of the 
tube is diminished to one-half its original length, and 
if the tube is of exactly even bore, it indicates a 
pressure of about fifteen pounds to the square inch 
in excess of the atmospheric pressure. 


LIQUEFACTION OF GASES. 125 


Faraday directs the manometers to be made of 
drawn-out tubing which is of greater diameter at the 
open than at the end which was to be closed. He 
directs that they be from eight to twelve inches long. 
They were calibrated and graduated by placing in 
them a drop of mercury. By careful manipulation 
this was moved from end to end of the tube and its 
length was marked off, step by step, for the whole 
length of the tube. This left the tube divided into 
lengths varying among themselves, but, as each cor- 
responded to the volume of the same drop of mer- 
cury, each length would give an equal volume. By 
having the tube larger at the base than at the top 
the readings for high compression became more deli- 
cate. The mercury was left in the tube to act as an 
index ; the upper end of the tube was sealed after 
the graduation was ended. 

In graduating the wide parts a larger quantity of 
mercury is prescribed for the operation, but the ori- 
ginal divisions on the upper part of the tube gave 
the basis for its entire division. 

In Faraday’s “ Chemical Manipulation,” American 
edition, 1831, page 608, quite elaborate directions are 
given for making these gauges. It will be evident 
that considerable accuracy is attainable with them. 
By such a tube he states that it is easy to read off to 
above one hundred atmospheres. 

In use he says that the compression tube should 
be bent in two places, giving three straight divisions, 
something like a letter N, and the little manometer 
is to be inserted in one of the divisions. 

Seventy-five years ago Faraday, with such appa- 
ratus, liquefied chlorine, cyanogen, ammoniacal gas, 


126 LIQUID AIR AND THE 


carbonic acid gas and some others, as described in 
this and the two preceding chapters. | 

The greatest care is to be recommended in carry- 
ing out these experiments. The tubes are very 
prone to explode, and if they do, the explosion is 
very violent. A tube will sometimes be in part re- 
duced to sand lke grains of glass. There were 
many such explosions in the early days of chemistry, 
and the experimenters wore glass masks. 

A very pretty experiment, which can be done ina 
straight closed tube, occurs in the liquefaction of 
chlorine from the hydrate. Chlorine hydrate, a 
compound of chlorine and water (Cl.OH;), is made 
by saturating water with chlorine gas and surround- 
ing the vessel containing it with ice. A somewhat 
strongly green-colored crystalline substance sepa- 
rates, which is chlorine hydrate. A more intense 
cold is needed to separate the crystals well. 

A quantity of the crystals is placed in a tube 
closed at the bottom and the upper end is sealed. 
On heating the hydrate it melts. A purse-like drop 
of chlorine forms near the surface of the liquid and 
hangs therefrom down into the liquid, constantly in- 
creasing in size until it falls to the bottom and the 
fluid is divided into two layers. At the bottom is 
liquid chlorine, above it is water. By slight addi- 
tional heat, if the other end of the tube is in a freez- 
ing mixture, chlorine can be distilled over, and will 
collect asa liquid in the cool end of the tube. The 
double bent tube may be used in this latter experi- 
ment. 

Sir Humphry Davy, in 1823, suggested a modifica-. 
tion of Faraday’s process. He would fill the tube 


LIQUEFACTION OF GASES. P27 


with the gas to be liquefied. Then a-little water, 
ether or alcohol is introduced, and the tube is sealed 
up. By heating the alcohol or other fluid, it gives 
off its vapor, and the pressure in the tube can there- 
by be brought up to any desired point within the 
limits fixed by the strength of the tube. In his own 
words, gas ‘“‘is in one leg of a bent sealed tube, con- 
fined by mercury.” The idea undoubtedly was to 
use such a tube as shown on page 124, and to place 
mercury in the intermediate bend, so as to shut off 
the water from the gas. 

The idea is rather ingenious, but we cannot ascer- 
tain that it led to any results. Gas has practically 
always been compressed either by the pressure pro- 
duced by its own evolution or by a pump or press, 
and Davy’s suggestion has not been utilized to any 
extent. 

Faraday thought so highly of the use of tubes in 
chemistry that a long chapter in his “Chemical 
Manipulation” is devoted to what he terms tube 
chemistry. It is illustrated with cuts representing 
many kinds of tubes, and the use of sealed tubes as 
here described for the liquefaction of gases forms 
only one of many applications which he describes. 

To orientate ourselves we must note that the book 
in question appeared long before Faraday did his 
final work on the liquefaction of gases. In 1845 he 
used the two condensing pumps, one working into 
the other, for compressing gases, and condensed 
them in tubes made of green glass, and sometimes 
fitted with brass cocks at the ends. Thus he de- 
parted,in 1845, from the simplicity of manipulation 
which distinguished his work of 1823. The book 


128 LIQUID AIR AND THE 


whose American edition is dated 1831 is an expo- 
nent of his earlier and simpler methods. 

Faraday has been used as a starting point in the 
history of the liquefaction of gases, because he not 
only is the first who did really thorough work on 
the subject, but because his investigations into the 
literature of the subject have greatly facilitated the 
fixing of the date of the work of the older investi- 
gators. 

The earliest ideas about the possibility of lique- 
fying gases were based very largely on the efficacy 
of pressure. The influence of pressure on lique- 
faction was not known, and various experimenters 
investigated it. M.le Baron Cagniard de la Tour 
attacked the subject, but in an inverted order. He 
demonstrated that liquids could be converted into 
gases of volume little more than twice their own. 
Had the scope of his work been properly appreciated, 
much trouble might have been spared more recent 
investigators. We know now that temperature is 
the essential thing in liquefying gas, and that pres- 
sure is altogether subsidiary to and dependent on it. 
There is no more impressive contrast to the work | 
of the early investigators who devoted all their ener- 
gies to the production of pressure for liquefying 
gases than the experiment described later (page 336), 
when the exterior surface of the simple tube of 
liquid air, exposed to exhaustion, drips with liquid 
air condensed from the atmosphere at atmospheric 
pressure by the intense cold. 

It was just before Faraday liquefied chlorine that 
the baron did his work and established La Tour’s 
law, that a liquid can be converted into a gas 


LIQUEFACTION OF GASES. 129 


which shall not exceed in volume the liquid itself. 
At ieast, his investigations gave the proof of this fact 
so nearly that the law is thus stated under his 
name. 

La Tour worked with sealed tubes, as did Fara- 
day, partly filling tubes with various liquids and ap- 
plying heat. He made a portion of the tube itself 
act as a manometer or pressure indicator. 

Before beginning his more accurate work on the 
small scale with glass tubes, he tried an experiment 
on the large scale which reminds one of Otto Van 
Guericke’s methods. The wonder is that he did not 
have an explosion. 

His original papers were published in the Aznales 
de Chimte et de Physique in 1822, and afford a good 
example of early methods of work. 

He first took the end of a cannon and filled one- 
third of its interior volume with alcohol. In it he 
placed what he calls a ball of silex, and closed the 
gun hermetically. On shaking it, the ball was 
checked in its motion by the liquid. He applied 
heat gradually, and eventually reached a point when 
the ball bounced about without obstruction, as heard 
from the outside. Water was tried, but did not 
work so well. Petroleum naphtha (?) and ether acted 
like alcohol. 

He unhesitatingly took it as proved that he had 
gasified alcohol, ether and petroleum naphtha in a 
space but three times their original volume. The 
fact that water did not give the same evidence 
operated in strong confirmation of his conclusions. 

The next point was to obtain ocular evidence of 
the gasification of a liquid in such a limited space. 


130 


LIQUID AIR AND THE 


Accordingly he sealed up in glass tubes ether, alco- 
hol and his petroleum naphtha, and, providing the 
tubes with long glass tails melted to them for han- 
dles, he heated them. As the heat rose the liquids 
expanded, sometimes to twice their original volume, 
and became very mobile, and suddenly disappeared 


a 


Dela Tour’s 
Apparatus. 


as they became converted into gas. 

The baron had this doubling of vol- 

ume firmly fixed in his mind, for he filled 
his tubes about two-fifths full and suc- 
ceeded in; his experiment. then @ie 
tried, with success, a tube nearly one- 
half filled, and another he filled a little - 
over one-half with the liquid. This tube 
burst. He was careful also not to have 
any air mixed with the vapor of the 
liquids in his tubes. 
, His apparatus as shown in the cut 
was of the simplest description. Mer- 
cury was introduced before the tube 
was sealed. It settled in the bend, c. 
The liquid was poured into the large 
tube or bulb, and after expulsion of 
air, if desired, by boiling, the bulb was 
sealed: (Ihe other end)2a;5 was" alsa 
sealed. Now, the mercury lying in the 
bend had air above it in the small tube, 
and if the air changed in volume, the 
mercury, by rising or falling, would 
indicate the extent of such change. 


The liquids in the bulb were heated. As the pres- 
sure rose, the mercury was forced up the small tube, 
and the diminution of volume of the air gave the 


LIQUEFACTION OF GASES. 131 


pressure. The air tube was so small in reference to 
the other that the mercury in rising made but little 
difference in the volume of the bulb. 

The liquids, it will be observed, could not increase 
but two or three fold in volume. Any space in the 
right hand division of the tube not filled with the 
liquid contained its vapor. As the heat increased 
the liquid disappeared, being completely gasified, 
and eventually all the gas from one volume of liquid 
was contained in the space to the right of the mer- 
cury, in volume but two or three times the original 
volume. 

The apparatus has various levels indicated in the 
original cut which the baron used in his description 
of his several experiments. Our illustration is a 
close reproduction of the original cut from the Ax- 
nales, and, like Faraday’s bent tubes, is an interesting 
example of early methods. The levels g, e’, 4, &, 
etc., indicate the levels assumed by the mercury as 
the conditions of volume of liquid, of gas, and the 
pressure in the tube varied. 

He gives the details of several experiments. The 
details of a single one will be sufficient to give an 
idea of his methods of work. 

In one experiment he filled the part of the tube 
marked 4,c,d,e, in the cut on page 130 with mercury. 
The space above the mercury in the wide part of the 
tube was partly filled with ether. When all was in 
place, the ends, a and f, were sealed by melting the 
glass witha blowpipe. Heat was applied and the ether 
expanded and became gas, forcing the mercury up to 
the mark, g. The narrow portion of the tube con- 
tained the compressed air, and from its reduction in 


132 LIQUID AIR AND THE 


volume he calculated the pressure to which the gasi- 
fied ether was subjected. 

The tube of larger diameter was four and a quarter 
millimeters (about one-fifth of an inch), the smaller 
tube was one millimeter (about one twenty-fifth of an 
inch) in diameter. Care was taken to have this nar- 
rower tube of even diameter. Other marks of level, 
e’, 6’, g’, are given by the baron to indicate how the 
experiment was performed with alcohol. 

The experiments with different liquids are de- 
scribed, and some of his calculations show to advan- 
tage the work of a careful observer cme sim- 
ple apparatus. 

One tube was two-fifths filled with alcohol sp. gr. 
0844. The liquid expanded to double its volume and 
then,.at a temperature: of 258°7° C. (497°7° F.), sud- 
denly. disappeared. The pressure was about 119 
atmospheres. Ether became gaseous at a tempera- 
ture of: 200°C. {(392° 'F.) with a pressure” Ofsa75 
atmospheres, the gas occupying twice the volume 
of the liquid. 

Water became gaseous in four times its bulk at a 
temperature of about 412° C. (773°6° F.), or that of 
melting zinc. <A little sodium carbonate had to be 
added to the water to prevent it from attacking the 
glass of the tube. Before he adopted this expedient 
his tubes broke when he used pure water in them. 

Many years later we find Cailletet repeating this 
last experiment with pure water in a metallic tube. 

As the vapors cooled, a cloudy appearance was ob- 
served, and the liquid, when the temperature fell 
sufficiently, suddenly reappeared. 

La Tour was very near to obtaining the evidences 


LIQUEFACTION OF GASES. 133 


of the intermediate state observed by Thomas An- 
drews (page 147). As.it was, he found that under the 
conditions a very wide departure from the law of re- 
lation of volumes of gases to their pressures existed, 
and he should be credited with a certain amount of 
important preparatory work in the liquefaction of 
gases, attacking the problem from the other end— 
effecting the gasification of liquids with very slight 
change of volume. 

In Colladon’s work, Geneva figures for the first 
time in the field we are treading. Later Pictet made 
the city by the lake famous by his liquefactions of 
gases. , 

Daniel Colladon, of Geneva, was the assistant of 
the great Ampére, and no apology is needed for in- 
serting an incident in his life, as told by Raoul Pictet 
in his work “ Etude Critique du Materialisme et du 
Spiritualisme.” . The last word is not to be rendered 
as our word “spiritualism ;” in the French language 
it refers to the operations of the mind and soul, not 
to the fraudulent manifestations of so-called medi- 
ums. 

Ampére had studied out his theory of magnetism, 
and had ordered apparatus to be made for its de- 
monstration. A distinguished audience assembled 
for the lecture, and at the last moment the appa- 
ratus arrived from the m:.ker. 

Those who are familiar with the Ampére theory 
of magnetism know how it is demonstrated by wire 
bent into helices, which are poised like compass 
needles and are subject to the movements of a com- 
pass needle when an electric current is passed 
through them. When the current passes, the solen- 


134 LIQUID AIR AND THE 


oids point north and south, the ends are attracted 
or expelled by one or the other pole of a magnet. 

Ampére began his lecture and gave his demon- 
stration “on the ‘blackboard; “He waseinst re. 
Pictet’s words, “superb, eloquent in the power of 
his conviction.” All present were delighted. Then 
the apparatus was taken in hand, and the practical 
proof of the theory was to be given. 

The solenoids were mounted and connected to the 
electric terminals so that the current passed. They 
refused to move. 

Ampére tried again, but in vain. The audience 
began to grow impatient. In the midst of the grow- 
ing inquietude the suffering scientist did his best, 
but could get no result. 

Ampére left the hall with Colladon. No one else 
was with them. They followed the Boulevard 
St. Michel toward the Seine, the tears running 
down Ampére’s cheeks. He went to the house of an 
intimate friend, and tried to distract himself with a 
game of checkers—an old distraction with him. 

Colladon now took the matter up, and began to 
reorganize the apparatus. He altered the method of 
suspension, substituting mercury cups for the solid 
contacts. He connected the electric terminals so 
that the currents passed, and all worked perfectly. 
It was eleven o’clock at night when he succeeded. 

He ran to where Ampére was trying to forget 
his sorrows in checkers, and called out to the great 
scientist, gloomily studying his game, “ It works, it 
goes, it moves!” 

Ampere seized his hat, and the two rushed off to 
the laboratory, where it was so late that the porter 


LIQUEFACTION OF GASES. 135 


wanted to exclude them from the laboratory. The 
scientist saw the experiments successfully performed 
as midnight crept over Paris. 

The lecture was repeated to a wildly enthusiastic 
audience with the beautiful experimental demonstra- 
tions which have done so much to immortalize the 
name of Ampére. 

As the audience left the hall, the Marquis de 
Laplace waited at the door until Colladon, the last 
to leave, was crossing the threshold. Laplace barred 
the way, extending his arms, and looked him in the 
face, and said: 

“Young man, you did not give it the least little 
touch? ”’ | 

Three or four years later, in 1828, Colladon, then 
corresponding member of the Academy of Science, 
performed many experiments in attempting to liquefy 
gases. His apparatus was almost exactly that of 
Cailletet, without the release cock, which was at the 
base of the success of the later experimenter. 

The dimensions of the apparatus, in the metric 
system, are quoted on the cut, which is an exact 
reproduction of one given by Prof. Pictet in his arti- 
cle on his work in the liquefaction of gases. 

Two shapes of the capillary tube are shown, for 
it was of importance to be able to introduce the end 
into a freezing mixture. The bending down of the 
end makes this more convenient than with a straight 
tube. : 

The tube within the steel reservoir was nearly an 
inch in external diameter. As it was exposed to the 
same pressure inside and outside, it could be made 
of thin glass. The thick walled capillary tube 


136 . LIQUID AIR AND THE 


ARTO SOO se wee pew ecececesecc-coe 


ny, 
Ba ccorcascce 


ome cconweerse A, 


pital ae aaa ey ——  y 


Ld 
eecossaa 2000 secs. 


2 TSE Sewers © 


D. Colladon’s Apparatus of 1828. 


which rose from 
it was from 006 
to 0°08 inch inter- 
nal diameter. The 
steel reservoir 
was about one 
and three-quarter 
inches in internal 
diameter and 
about five and a 
half inches high. 
A steel -reser- 
voir, B, held mer- 
cury. Bya tube, 
C, counection 
could be made 
with its interior. 
An extension, 4 
A, was bolted 
firmly :to’ Tit.aaee 
glass gas tube, 
T T, open: at the 
bottom, with a 
long capillary 
tubese2"%, “rising 
from its upper 
end, was mounted 
and inclosed in 
the mercury Cis- 
tern as shown. 
The end of the 
capillary tube 
was closed. A 


LIQUEFACTION OF GASES. 137 


limited amount of mercury only was required, as 
water could be used above it in the reservoir, 2. 

The capillary tube nearly fitted the long tube 
through which it passed, and the joint between metal 
and glass was made secure by gum lac. 

Colladon worked at —30° C. (—22° F.) and 4oo 
atmospheres pressure, without result. 

The principal parts of his apparatus are still in ex- 
istence, carefully preserved in the offices of the So- 
ciété genevoise pour la construction des instruments 
de physique, in Geneva, Switzerland. An accurate 
sectional view of the same, reproduced here, is given 
in the Annales de Chimie et de Physique, fifth series, 
vol. xiii., plate facing page 288. 

Thilorier applied the pressure produced in the 
generation of a gas to its own liquefaction. His 
pattern in this was Faraday,.and he has been fol- 
lowed by Pictet and some others. He worked upon 
carbon dioxide gas, the gas familiar to all as the one 
which escapes from effervescing liquids. A pair of 
cast iron vessels were employed. In one the gas was 
generated, in the other it was received after genera- 
tion, and the pressure alone was relied on to produce 
the liquefaction. He had no idea of applying refrig- 
eration. 

Producing liquid carbon dioxide on the large scale, 
he found, on releasing it from pressure, that the now 
familiar solid carbon dioxide was produced in snow- 
like masses. This gives an admirable example of 
the cold of a boiling liquid. The liquefied gas boils 
so energetically that it renders a quantity of heat 
“latent,” or uses up heat energy, and the chilling of 
it is so great that some of it becomes a solid. 


138 LIQUID AIR AND THE 


When Thilorier first observed this, he attributed 
it to the moisture of the air, and thought that the 
white solid was snow. A committee of the French 
Academy of Science examined it and found that it 
was carbon dioxide gas solidified. 

The original Thilorier apparatus for liquefying car- » 
bon dioxide was made of cast iron, as has just been 
stated. In 1835 one of them blew up at the Ecole 
de Pharmacie, Paris, and tore off both legs of the un- 
fortunate operator, M. Hervy. The use of the cast 
iron apparatus was proscribed on account of this ac- 
cident. Mareska and Donny then modified the appa- 
ratus by constructing it without employing cast iron 
for generator or receiver. 

In Liebig’s chemical letters is given an account of 
this accident, which, as expressed in the words of the 
great German chemist and writer, is ies quoting 
in full: 

“A melancholy accident occurred at Paris which 
proved the extreme danger of the preparation of 
liquid carbonic acid by the action of sulphuric acid 
on bicarbonate of soda, which is accompanied by a 
strong disengagement of heat. Just before the com- 
mencement of the lecture in the laboratory of the 
Polytechnic School, a cast iron cylinder two feet and 
a half long and one foot in diameter, in which car- 
bonic acid had been developed for experiment 
before the class, burst, and its fragments were scat- 
tered about with the most tremendous force; it cut 
off both the legs of the assistant, and the injury was 
followed by his death. We can scarcely think with- 
out shuddering of the dreadful calamity which the 
explosion of this vessel, formed of the strongest cast 


LIQUEFACTION OF GASES. 139 


iron and shaped like a cannon, would have occa- 
sioned in a hall filled with spectators, and yet the 
apparatus had been often used for the same experi- 
ments, which naturally banished all idea of danger.” 
(Liebig’s “Familiar Letters on Chemistry,’ London, 
Bohl gletter x:, pares. 130,-131:) 

The Thilorier improved apparatus is shown in the 


Thilorier’s Apparatus for Liquefying Carbon Dioxide. 


illustration. The rignt hand vessel, carried by trun- 
nions, is of lead, inclosed in copper, with iron hoops 
or bands. It is connected by a tube with screw 
joints and connections as shown to a cylindrical re- 
ceiver of similar construction. The tube connecting 
the two is of copper and has two stopcocks. The 
size of the apparatus as made may be gauged from 


140 LIQUID AIR AND THE 


the fact that the generator was of 6 to 7 liters capa- 
city, or nearly 2 gallons. 

To use the apparatus, the two vessels were first 
disconnected. Eighteen hundred grammes of sodium 
hydrogen carbonate (common baking soda), with four 
liters of water, were placed in the generator. A cyl- 
indrical vessel containing one thousand grammes of 
sulphuric acid was placed init. In some construc- 
tions this vessel had a wire-like projection from the 
bottom designed to keep it in position, as Shown in 
the cut. 

The generator, which is the left hand vessel in the 
cut, was closed, the top being screwed on and the 
cock closed. By rocking and inclining it, the acid 
was discharged with some degree of control upon 
the sodium carbonate solution and upon the undis- 
solved salt, and the gas was produced. 

The generator and receiver (the right hand vessel) 
were now connected by the copper tube, the cocks 
were opened, and the gas rushed over into the re- © 
ceiver. A minute of time was allowed for the es- 
tablishment of equilibrium, the faucets were closed, 
and the vessels were again disconnected. 

The residual gas inthe generator was blown off, 
the top was removed, and the whole operation as 
described was repeated. Five to seven repetitions 
were required to produce four liters, or a little over 
a gallon, of liquid carbon dioxide. 

It is calculated that, with the apparatus charged as 
described, there was room in the generator for about 
one liter or a quart of gas. At the temperature of — 
4o° C. (104° F.) the pressure would rise to one hun- 
dred atmospheres. 


LIQUEFACTION OF GASES. I4I 


Thilorier did some good work on liquid carbon 
dioxide. As far back as 1835 we find a paper of his 
in the Axnales de Chimie et de Physique on the 
properties of the liquefied gas. The extraordinarily 
high expansion of the liquid is spoken of, and the 
figures as he determined them are given. He finds 
it insoluble in water and in fatty oils. He gives a 
freezing mixture based on its employment, suggest- 
ing a mixture of liquid carbon dioxide and ether. 

He found that this gave a frigorific agent of 
great power. By placing liquid carbon dioxide in a 
vessel provided with an outlet in the form of a blow- 
pipe jet, he was able to produce local cooling effects. 
A jet of vapor would rush out, and would have great 
chilling powers. The arrangement he terms a cha- 
lumeau de frotd—a cold blast blowpipe. He hopes 
for still better effects from a mixture of carbon 
disulphide and liquid carbon dioxide. 

It is interesting, forty to fifty years later, to find the 
idea of producing cold by a jet from a liquefied gas 
again brought forward. Cailletet proposed to utilize 
the latent heat of liquid ethylene in this manner. 
The subject will be found treated on page 108 of this 
work, and Dewar used an escaping jet of liquefied 
hydrogen to freeze air and oxygen into solid white, 
icelike masses, as described on page 269. 

Eleven years after Thilorier had devised his dan- 
gerous apparatus, anew one was produced by an 
Austrian scientist, which apparatus was compara- 
tively safe. Ina pump was the compressor, and a rel- 
atively small receiver, artificially cooled, took the 
place of Thilorier’s large vessel. It was in 1845 that 
the apparatus was produced, and subsequent changes 


142 LIQUID AIR AND THE 


materially improved it. Johann Natterer, of Vienna, 
was its originator. 

The apparatus consisted of a vertical compression 
pump actuated by a crank with flywheel. The pump 
was mounted in an inverted position and delivered 
the gases which it compressed upward from its 
highest point, which in its inverted position was 
really the bottom of the pump barrel. It was sur- 
mounted by a wrought iron reservoir of about one 
liter capacity which was strong enough to withstand 
a pressure of 600 atmospheres. 

The liquid gas reservoir, slightly pear shaped, was 
surrounded with a basin of copper, designed to hold 
a cooling mixture. The pump hadasolid piston. At 
the point where the pump barrel connected with the 
reservoir wasa valve which opened upward. The gas 
to be liquefied was conducted to the lower end of the 
pump barrel, where a tube entered it far enough from 
the end to be above the solid piston as it reached its 
lowest point of descent. 

An important modification was introduced by 
Bianchi. He surrounded the pump barrel with a 
jacket of metal, and let the liquid which drained from 
the refrigerating basin flow down and fill this jacket, 
whence it could be drawn from time to time by an 
outlet cock. Thus the pump barrel was cooled and 
a better working insured as regards the lubrication. 
The compression of a gas produces heat, and this 
dries up most lubricants. The gas also was thus 
delivered at a lower temperature to the reservoir, 
which in itself was an advantage. Those who have 
used compression pumps are familiar with the 
heating effect, which can be observed even in a 


LIQUEFACTION OF GASES. 143 


bicycle tire pump when inflating a pneumatic tire. 
A second jacket surrounded the piston rod, which 
jacket received the melted material flowing from the 
refrigerating basin, so as to cool the piston rod 
directly. 

The liquid gas reservoir could be unscrewed from 
the pump and carried about. The valve. at its 
base closed and prevented any escape of gas. At 
its top the reservoir was provided with a cock by 
which the gas could be drawn off. 

The gas is made in a generator, and may be first 
introduced into india rubber bags, which supply it 
to the apparatus, as shown inthe cut. The drying 
apparatus, shown in the cut, is a Wolf’s bottle (three- 
necked bottle) charged with a drying agent. The 
drying agent may be sulphuric acid, chloride of 
calcium, or some other of the regular materials used 
by chemists to remove water from gases. 

The apparatus, which is a sort of classic, shows 
every sign of being designed to insure perfection 
rather from a mechanical than scientific standpoint. 
Simply for lecture demonstrations it is rather effect- 
ual, and is considered safe—something which can- 
not be said of some of its predecessors. The early 
experimenters, from Northmore down, have been 
troubled by explosions which culminated in the kill- 
ing of aman, as already alluded to in the description 
of Thilorier’s apparatus. 

In the cut the entire apparatus is shown mounted 
and ready for work, and a sectional view on a larger 
scale shows the interior of the pump, gas reservoir 
and connections. A is the liquid gas reservoir, with 
its escape valve, 7, x, for drawing off the liquid, and 


144 LIQUID AIR AND THE 


its self-acting base valve, S, through which the gas 
enters. It will be seen that, to draw off liquefied 
gas, the reservoir must be inverted. B is the cool- 


Natterer’s Apparatus for Liquefying Carbon Dioxide. 


ing basin; , 2,0, the drainage pipes and cock; C, 
the cylinder or pump barrel cooling jacket; and be- 
low is seen the small jacket for cooling the piston 


LIQUEFACTION OF GASES. 145 


rod. The piston rod, ¢, with pitman, 4, works in 
the slides, P, Q, in the massive metal frame. The 
gas from the bag, A, dried in its passage through 
pie bottle, /, enters by the’ pipe; A. 

It is Natterer who is celebrated for his liquefac- 
tion of nitrous oxide gas on the large scale, and who 
mixed the liquid with bisulphide of carbon for the 
production of an intense yet manageable refrigerat- 
ing agent for scientific uses. 

For determination of low temperatures Natterer 
used a thermometer filled with phosphorus chloride. 
This he told orally to Prof. Wroblewski or Ols- 
zewski (Wzedemann’s Annatlen, 1883). 

The old apparatus was quite troublesome to use. 
It required one to one and a half hours’ intermittent 
pumping to complete the operation. The piston rod 
had a way of heating, and this interfered with its 
lubrication; so that the operator had to stop from 
time to time to oil it, and this gave it a chance to 
cool. 

When the receiver was two-thirds full 450 grammes 
of liquid carbon dioxide could be taken from it. 

In the Leipzig Journal fuer praktische Chemie for 
1845 is to be found a description of the early form 
of Natterer’s apparatus, unimproved by the auxiliary 
cooling jackets shown in the more modern apparatus 
illustrated by us. The article is by Prof. Pleischl, 
' and is quite quaintly expressed, or at least reads so 
in the light of over half a century’s developments. 

Prof. Pleischl notes the danger incident to the use 
of Thilorier’s apparatus, and speaks of the death of 
Hervy, who.was killed by its explosion some years 
previously. He says that his talented young student 


146 LIQUID AIR AND THE 


Johann Natterer had succeeded in liquefying carbon 
dioxide with an air pump, and that led to the con- 
struction of what is known as Natterer’s apparatus, 
The great safety of the new pumping system is quite 
enthusiastically commented on, and more notes of a 
public exhibition given on March 11 are embodied, 
at which exhibition carbon dioxide snow produced 
by Natterer’s process was shown to adelighted audi- 
ence. It was mixed with ether and used to freeze 
mercury, among other experiments. 

Natterer made great efforts to liquefy the more 
permanent gases, but without success, and seems to 
have greatly regretted that better fortune did not 
attend his work. He carried his pressures up to 
nearly 4,000 atmospheres, or double the pressure pro- 
duced in a cannon by the exploding powder. Some 
of his work is described in the Wiener Berichte, vols. 
v., vi. and xii. A rather complicated screw pressure 
apparatus is described and illustrated, by means of 
which he performed his high pressure experiments 
and determined quantities of data of the compression 
of gases under pressure. In vol. xi. of the Berichte 
he expresses his regret at not succeeding in lique- 
fying gases. 

Had he given the same attention to cooling his 
gases that he did to compressing them, he might 
have had a different tale to tell. The realization of 
all that the critical temperature means has given the 
liquefaction of gases its new aspect, and has led to 
the recent triumphs. 

Far too little attention is given to Natterer’s ex- 
cellent work. He subjected gases under perfect 
control and visibility to most enormous pressures, 


LIQUEFACTION OF GASES. 147 


and certainly to that extent helped to prove the doc- 
trine of the critical temperature. 

In 1888 Amagat, carrying pressures up to 3,000 
atmospheres, got some discrepancies in his 
compression figures as compared with 
those of Natterer. 

The work done by Thomas Andrews, 
of Belfast, in 1861 to 1870, as determining 
the existence of a critical state, is classic, 
and his simple apparatus is shown in the 
cut. A small glass tube contains the gas; 
a short column of mercury closes the tube 
below the gas; the upper end of the tube 
is sealed. The tube passes through a brass 
block, Z, which is held by screw bolts on 
the end of a copper tube, X. A perforated 
block with screw thread cut in the per- 
foration closes the lower end, and a steel 
screw, S, passes through the hole and 
closes it. All is packed so as to secure 
absolute tightness. The copper tube is 
filled with water. On screwing in the steel 
screw, the water is forced up against the 
mercury in the glass tube, g, and the mer- 
cury,in its turn, is forced up and the gas 
is reduced in volume, the object of the 
mercury being to cut off the water so that andrews’ 
there shall be no action of the water on Apparatus 
the gas. pee 

‘ ; pressing 

To use mercury in this way, the tube, g, “Gases. 
has to be of small caliber, or else the mer- 
cury would drop out. But another reason obtains. 
The steel screw is small, and the tube must be of 


148 LIQUID AIR AND THE 


the volume, or not much in excess of the volume, of 
the portion of the screw which can be screwed in 
and out. 

By screwing in the screw the pressure could be 
raised to 500 atmospheres. Sometimes the tube was 
bent downward, so that its end could be placed in a 
freezing mixture, as shown in Colladon’s apparatus, 
page 136. 

Other varieties of the apparatus are shown in his 
paper published in the Tvansactions of the Royal 
Society of England for 1869. 

In his early work he had used the compression 
produced by the electrolysis of water. If two ter- 
minals of an electric circuit of about two volts or 
more difference of potential are placed in a vessel 
of acidulated water, or of a solution of various chem- 
icals, such as sodium hydrate or potassium hydrate, 
gaseous oxygen will be liberated from one terminal 
and gaseous hydrogen from the other. 

The illustration shows a simple arrangement for 
carrying out the experiment. In the background is 
seen the battery. In the foreground is the decom- 
position vessel, with two spiral terminals or elec- 
trodes immersed init. Only the spiral ends of the 
electrodes are bare. The other parts are covered by a 
tube of india rubber. The bare ends are inclosed in 
inverted test tubes, themselves filled with the solu- 
tion. When the battery is connected as shown, 
bubbles rise from the wires, and hydrogen and oxy- 
gen gases collect in the test tubes. 

Now, if such electrodes with some solution were 
introduced into a hermetically sealed and very 
strong vessel, the two gases would be evolved and 


LIQUEFACTION OF GASES. 149 


enormous pressures could be generated by the quiet 
effects of the electric current. This is what Andrews 
did in his early work. With such apparatus he re- 
duced oxygen gas to one three-hundredth of its 
volume. 

In his later work, using apparatus on the principle 


Electric Decomposition of Water. 


described above, and using strong capillary glass 
tubes for the compressed gas, supplementing high 
pressure by cold of —106° C.(—159° F.), he reduced 
air to. one six-hundred and sixty-fifth part of its vol- 
ume. He got no result with any of what he called 
the six non-condensible gases. 


150 LIQUID AIR AND THE 


These were hydrogen, oxygen, nitrogen, carbonic 
oxide, nitrogen dioxide and marsh gas. 

One of Andrews’ principal papers, utilized above, 
is published in the 7vansactions of the Royal Society, 
as quoted, with very elegant cuts of the apparatus. 
It appears in a translation in the Aznalcs de Chimie ct 
de Physique of 1870. 

Clerk Maxwell was much interested in Andrews’ 
work. One of his letters alluding to Andrews’ ex- 
periments, and addressed to the scientist, and be- 
stowing his encomiums on his explorations into the 
realm of gases, is given in Tait and Brown’s memoir 
on the life of Andrews. 

The date of Andrews’ work is generally put about 
1862, one of his principal papers being published 
twelve years after his researches were made. 

We have now reached a period whose history de- 
mands a somewhat different treatment. Up to the last 
date mentioncd certain gases had resisted all attempts. 
at liquefaction. Those which had been liquefied had 
been the subject of experiments on the small scale, 
and the efforts of investigators had been directed to 
the attaining of purely theoretical results. Two in- 
vestigators now appear who profoundly modified 
the views of the scientific world. Pictet and Cail- 
letet demolished the old division of permanent gases, 
and in doing so had a close race for priority. The 
French scientist Cailletet was awarded the priority by 
afew days only. But the work of the two men was 
so different in its scope and results that they should 
be considered hardly as rivals. Cailletet, by acci- 
dent, produced mists in a. small glass tube. These 
mists were due to the momentary liquefaction or 


LIQUEFACTION OF GASES. I5!I 


reduction to the vesicular state of the gases con- 
muned. _ Pictet, on the other hand,- directed “his 
efforts from the first to producing a tangible quan- 
tity of liquefied gas. He was the first to secure this 
result; he was the first to produce a jet of liquid 
oxygen; he established the system of cascade or 
closed cycle refrigeration that has been the guiding 
principle for some twenty years of laborious investi- 
gation. Basing his work on Pictet’s cycles, Dewar 
filled the Royal Institution laboratory with machin- 
ery and produced liquid gases by the gallon. Wro- 
blewski and Olszewski combined Colladon’s and 
_Cailletet’s methods with Pictet’s cycles for the at- 
tainment of their results. 

It should be felt that Pictet and Cailletet are to 
be placed side by side, and that no question of prior- 
ity should be appealed to as existing between them. 


LIQUEFACTION OF GASES. 153 


CHAPTER Re VITk 
RiOuLebICEErt: 


The life of Raoul Pictet—His education—His ice machines— 
Disputed priority—Honors awarded—His apparatus for 
liquefying gases—Description of its operation—Tempera- 
tures of the cycles of operation—His dispatch of Decem- 
ber 22, 1877, to the French Academy—Regnault’s state- 
ment—Hydrogen—His dispatch of January 11, 1878, to 
the French Academy—Olszewski’s comments on the 
hydrogen experiment—Pictet’s arrangement of pumps— 
His desire to produce liquid oxygen in quantity—Com- 
ments on his work—-The /iquzde Pictet. 


Raoul Pictet was born in Geneva, Switzerland, on 
August 4, 1846. He finished his studies in the 
Academy of Geneva when eighteen years old, and 
published some memoirs on binocular vision and on 
the resistance of the air. He went to Paris, and, al- 
though a foreigner, was received as a student at the 
Ecole Polytechnique in that city. He also took courses 
in the College of France, and in the Sorbonne. 
There the young student became the friend of the 
greatest French scientists, Wurtz, J. B. Dumas, Reg- 
nault, Quatrefages and others. He received recog- 
- nition from a most distant quarter, when the Saint 
Petersburg Academy of Sciences crowned his in- 
vestigations of binocular vision and offered to pub- 
_ lish all of his researches in full. 

Three years were devoted in great part to the 


1§4 LIQUID AIR AND THE 


study of thermodynamics. He made during the in- 
terval several long tours, and then returned to 
Geneva. 

At the age of twenty-five he enterea the service of 
the Viceroy of Egypt. He was charged with estab- 
lishing a course of instruction in experimental phy- 
sics at the Ecole Superieure, in Cairo. While thus 
oecupied he gave a good example of his aptitude for 
languages, acquiring Arabic in a few months’ study. 

Three years were passed in Egypt, and his life 
there gave rise to various interesting memoirs. The 
atmospheric phenomena of the desert, solar action, 
dust, whirlwinds and eddies, the temperature and 
floods of the Nile, were among the subjects studied 
and written on. He organized hunting expeditions 
into the interior, enriching with the spoils the 
museums of Cairo and of Naples. | 

The poisonous reptiles of the Nile regions, one of 
whose ancestors may be assumed to have inflicted 
the death wound on Cleopatra, attracted his atten- 
tion, with a view to combating their venom in the 
human system. He collected snakes, and studied 
their poison in its action on the animal system. At 
one time he had four hundred specimens of Nile 
snakes in captivity. The natives of the region, it 
is said, still speak of the Geneva scientist who strove 
to diminish the deaths due to serpents’ bites. 

In 1877 Geneva claimed her son, and he accepted 
there a chair of physics and mathematics in the 
University of Geneva. He had for some years made 
ice machines, and had invented a process for freezing 
large areas of ice for skating, being a skater of no 
mean order himself. London, Manchester and other 


LIQUEFACTION OF GASES, 155 


places saw skating rinks constructed on the Pictet 
system. 

On his establishing himself once more in his native 
city, he was well prepared to begin his work on the 
liquefaction of gases. His work is detailed else- 
where. His friend Prof. Dufour, of the University 
of Lausanne, describes a visit made by special invi- 
tation to the buildings of the Société genevois pour 
la construction des instruments de physique. The 
visitors were a number of professors and scientists 
from Lausanne, the date was December 29, 1877, 
and Pictet showed them the liquefaction of oxygen. 

It will be seen that his early work in the produc- 
tion of low temperatures was in the practical line, 
and, therefore, on the large scale. This it was 
which gave his liquefaction of gases such value. He 
was not content to produce an infinitesimal amount 
of liquid. The desire to produce tangible quantities 
was ever present in his mind. As regards the 
method, it was based on practically successful pro- 
cesses. The engineer’s mind appeared in the work- 
ing of his cumulative cold-producing circuits, and he 
established a system which has done service for over 
twenty years of investigation in England, Holland, 
Poland and Germany. 

As will be seen by those who follow the dates 
given in this book, there was a close coincidence be- 
tween the dates of Pictet’s and of Cailletet’s liquefac- 
tions of oxygen. This was the origin of hot disputes 
waged by the political dailies, for in Europe all sorts 
of pretenses are seized upon for political effect, 
The methods followed and apparatus employed by 
the two scientists were so radically different that at 


156 LIQUID AIR AND THE 


last Cailletet protested, the war ceased, and an inti- 
mate friendship was formed between the rivals that 
was never broken. Regnault interested himself in 
the work he had so long followed, and informed the 
Academy of France that Pictet’s system of cumula- 
tive cold-producing circuits, to his knowledge, dated 
back five years, and that the experiments might have 
been performed five years earlier had events favored 
the work. 

The dispute was ended, and Pictet received the 
decoration of the Legion of Honor. France, as 
always, was generous to the foreign rival for scien- 
tific honors. 

The mechanical theory of heat was, about this 
time, investigated by him in union with M. Gustave 
Cellérier for eighteen months. The study was so 
intense that Pictet nearly broke down in health on 
the completion of the work. 

In 1878 he received from the International Expo- 
sition at Paris the gold medal, and in the same year 
the Royal Institution of England gave him the 
Davy medal. 

In 1880 he went to Berlin, and there established a 
low temperature laboratory. The study of frigo- 
therapy was taken up, and the purification of chemi- 
cals by intense cold was worked upon. 

The cities of Antwerp and of Rome have recently 
honored him by diploma and medal of honor. In 
1895, the Société Industrielle du Nord de la France 
gave him its grand medal of honor at Lille. . 

His life has been written from the standpoint 
of a dear friend by Prof. Henri Dufour, of the 
University of Lausanne, Switzerland. To him the 


LIQUEFACTION OF GASES. 157 


author of this book is indebted for copious notes on 
the life of Pictet, and interesting accounts of the 
personal traits of the distinguished scientist, who 
knows how to charm children by feats of legerde- 
main as well as to interest and delight the world of 
scientists by his achievements in physics and in the 
realm of low temperature. 

He has entered the field of intellectual and moral 
philosophy in his treatise entitled Aztude Critique du 
Matcrialisme et du Spiritualisme par la Physique Ex- 
perimentale. This is a large octavo, and investigates 
the relation of material energy and mental opera- 
tions most interestingly, and is a scientific protest 
against doctrines leading to the depression or de- 
spair which sometimes seems to obtain a foothold 
among scientific students. 

Pictet’s apparatus by which he succeeded in lique- 
fying oxygen is described in the Comptes Rendus, 
vol. Ixxxv., page 1214. The illustration we give is 
substantially identical with the one given in the 
Comptes Rendus, except that it is completed by the in- 
troduction of the gas burner for heating the oxygen 
retort, and that a manometer or pressure gauge and 
outlet cock are shown at R, WV. 

The Pictet apparatus, as shown, deserves especial 
attention because it is the original of a type which 
only now encounters in self-intensive processes a 
really efficient rival. It was far in advance of its 
time. Apparatus of its type was added to the Col- 
' ladon apparatus by Wroblewski and Olszewski for 
their work. Dewar employed it in his Royal Insti- 
tution researches, and the extensive apparatus in the 
Leyden University cryogenic laboratory is based 


158 LIQUID AIR AND THE 


upon its lines. This apparatus was the first to pro- 
duce a stream of liquid oxygen, and it cannot be 
awarded too high a place in the history of low tem- 
perature experimentation and research. 

L isa wrought iron retort calculated in the origi- 
nal Pictet apparatus to resist 500 atmospheres pres- 
sure. Subsequently, it is said to have been made 


Raoul Pictet’s Apparatus for Liquefying Gases. 


stronger, so as to be able to withstand three times 
this pressure. A weighed amount of potassium 
chlorate was introduced by the opening, P, which 
was then closed. On heating it by the lamp, O, the 
quantity of oxygen to give any desired pressure was 
produced, such quantity being determined by the 
- weight of potassium chlorate employed. 


LIQUEFACTION OF GASES. 159 


The tube, J7, was thus filled with oxygen at a pres- 
sure regulated by the weight of potassium chlorate. 
Pressure was thus produced, which is one element 
of the process of liquefaction. The next step is the 
cooling of the compressed gas. 

The condenser jacket, C, contains liquid sulphur 
dioxide. This tends to evaporate and to produce 
thereby great refrigeration. From the upper end of 
the jacket, C, a pipe goes to the pumps, 4 and B. 
These pump out gaseous sulphur dioxide. The 
liquid sulphurous oxide in C boils, therefore, with 
greater rapidity than ever, and produces greater 
cold. The gas goes through the pumps and is com- 
pressed by them in the condenser jacket, D. The 
outlet of this condenser jacket, D, is a narrow pipe, d, 
which, being of small diameter, produces the requi- 
site pressure to condense the sulphur dioxide to a 
liquid. Through the condenser jacket, D, a pipe 
runs, and cold water passing through this pipe cools 
the sulphur dioxide as it comes heated by compres- 
sion from the pumps, 4 and JB. 

The upper system of pumps and cooling arrange- 
ments is almost in exact duplication of what has just 
been described, except that liquid carbon dioxide 
takes the place of liquid sulphur dioxide, and the 
liquid sulphur dioxide under exhaustion takes the 
place of the cold water. 

The condenser jacket, 4, contains liquid or solid 
carbon dioxide, which constantly evaporates. The 
pumps, & and /, pump gaseous carbon dioxide out 
of the upper end of 7 and condense it in the tube, 
K, where it is cooled by the boiling sulphur dioxide. 
The small pipe, 4, creates the requisite back pressure | 


160 LIQUID AIR AND THE 


for the liquefaction, and a constant circulation is 
thus maintained, and the boiling carbon dioxide 
keeps the tube, JZ, inclosed in the condenser jacket, 
H, at a very low temperature. 

The following figures are given in the Comptes 
Rendus as the data of the first successful eae at 
liquefying oxygen: 

The sulphur dioxide liquefied in D at a pressure of 
two and three-quarters atmospheres, and produced 
by its evaporation in the jacket, C, a temperature of 
—25° C. (—13° F.) The carbon dioxide liquefied 
in Cat a pressure of five atmospheres and a tempera. 
ture of —65° C.(—85° F.) The tube, J, by the 
evaporation of the cold carbon dioxide, was kept 
at a temperature of —140° C. (—220° F.) 

In the improved apparatus, the tube, 1/7, was made 
of copper, and the liquefied gas was withdrawn at JV; 
but in the apparatus of 1877, as shown in the Comptes 
Rendus, the tube in question was unprovided with a 
faucet, and its lower end was within the condenser 
jacket, 7. The tube was one meter or a little over 
a yard long. 

In the original experiments, which now may be 
considered historic, the pumps were worked for sev- 
eral hours circulating the sulphur dioxide and car- 
bon dioxide. A 15 horse power engine was employed 
to drive them. Meanwhile oxygen was being evolved, 
and the pressure was brought up to 320 atmospheres. 
Then the cock at P was suddenly opened, and the 
sudden expansion of the tremendously compressed 
and very cold oxygen absorbed so much heat ener- 
gy, rendering the heat latent, that the temperature 
fell still further, the oxygen was liquefied in part, 


LIQUEFACTION OF GASES. 161 


and the tube, JZ, was filled to one-third of its length 
with the liquid. The tube being of 1 centimeter (0°4 
inch) internal diameter, it will be seen that this was 
a considerable quantity of oxygen—about 22 cubic 
centimeters or 14 cubic inches of the liquid. 

On inclining the tube by raising the lower end, the 
liquid rushed out of the orifice at P (‘et jaillisse par 
l’orifice en inclinant lappareil”). It will be remem- 
bered that in the original apparatus there was no 
way of opening the lower end of the tube, which 
was closed and within the condenser jacket, 7. 

Pictet’s dispatch announcing the success of his 
experiment, on which so much time, thought and ex- 
pense had been lavished, was received by the French 
Academy of Sciences on December 22, 1877, at 8 P. 
M. It was as follows: 

“Oxygéne liquéfié aujourd’hui sous 320 atmo- 
spheres et 140° de froid par acide sulphureux et 
carbonique accouples. 

iene, 
“ RAOUL PICTET.” 
(TRANSLATION. ) 

“ Oxygen liquefied to-day under 320 atmospheres 
and 140° of cold by suphurous and carbonic acid 
working together. 

“Signed, 
sh AQUI RICTED.” 

The terms sulphurous acid and carbonic acid are 
synonyms for sulphur dioxide and carbon dioxide. 

The substitution of the open copper tube J/ for the 
closed one and the use of the manometer, &, and cock, 
NV, are later modifications. The temperature of the 
oxygen generating retort, Z,is now put at 485° C. 


162 LIQUID AIR AND THE 


a af 12747 


| 
j 


Annaratn 


Pictet’s Gas Tignleariad 


7 


LIQUEFACTION OF GASES. 163 


{905° F.) The manometer in the course of the conden- 


sation rose gradually until it indicated a pressure in L 
and J of 500 atmospheres. The gas began to liquefy 
and the pressure fell to about 320 atmospheres. On 
opening JV, the oxygen rushed out under the great 
force of the pressure with violence, looking like a 
dazzling white pencil. The escape lasted for 3 or 4 
seconds; the manometer showing some 400 atmo- 
spheres, which rose again and again fell when lique- 
faction occurred. 

The large cut shows the general disposition of 
Pictet’s apparatus as installed in Geneva. 

Fand fare two boxes packed with non-conducting 
material, and in each of these are two concentric 
tubes constituting a condenser of the Liebig type. 

In F is the oxygen liquefaction tube surrounded 
with another tube through which the carbon dioxide, 
solid, liquefied and partly gaseous, circulates. This 
corresponds to 4 and /of the diagram on page 158. 


~ In @ is the carbon dioxide tube, where the gas 


from the outside tube in / is cooled by boiling sul- 
phurous oxide, which is in a tube inclosing and 
concentric with the carbon dioxide tube. These are 
Kand C of the diagram. 

G is a gashclder filled with carbon dioxide gas. 
K isareservoir of liquid sulphurous oxide. VP are 
the pumps, and # is the oxygen retort. 

A moment’s inspection of the cut, after study of the 


cut on page 158, will suffice to give a full understand- 


ing of the operation of the apparatus. 

It was no easy matter to obtain the small quantity 
of liquid gas that greeted Pictet’s vision on the 
twenty-second of December, 1877—the first sight of 


104 LIQUID AIR AND THE 


liquid oxygen in quantity that ever was granted to 
man. Regnault told the French Academy that he 
had assisted Pictet and De la Rive five years before 
the date of the liquefaction in experiments on lique- 
fying gases, and the work of five long years reached 
only then its culmination. 

Pictet examined with a polariscope the escaping 
jet of liquid oxygen as it rushed violently out of his 
tube, and thought that he obtained evidences of the 
presence of solid particles in the stream. 

Pictet did not rest here. The few cubic inches of 
liquid oxygen which he had produced acted as an 
incentive to go further, and he endeavored to liquefy 
hydrogen. 

The details of the experiment are given in the 
Comptes Rendus, vol. \xxxvi. They are contained in a 
dispatch from Geneva, followed by a letter. 

He wished to make his hydrogen by heating 
a solid substance in a retort, so as to preserve 
the general system of his oxygen method. <Accord- 
ingly, he employed a mixture of potassium formiate 
and potassium hydrate. This mixture, he says, gives 
pure hydrogen, free from water or carbon dioxide, 
and leaves a non-volatile residue. 

On applying heat to his retort, the pressure ran up 
to 650 atmospheres and then remained stationary. 
The temperature of the gas tube was about —14 9° 
C. (—220° F.) Enough gas was generated to meas- 
ure 252 liters at 0° C. (32° F.) .The cock was opened 
and what is described as a steel blue jet escaped with 
a sharp hissing sound. A length of 12 cm. (about 5 
inches) of the jet was opaque. The jet struck the 
floor with a sound like hail. The hissing sound 


LIQUEFACTION OF GASES. 165 


changed its character until it resembled the noise 
produced when metallic sodium is thrown upon 
water. The pressure ran down to 370 atmospheres 
and the delivery became intermittent, the tube or 
cock being choked. For over fifteen minutes the 
delivery by the jet occurred in intermittent dis- 
charges. 

The liquefaction of hydrogen has been felt to be 
open to doubt. The fact that the temperature as 
given is entirely insufficient, at any pressure, to 
cause liquefaction does not at all invalidate the expe- 
riment. The release from high pressure of the gas, 
bringing about its expansion, rendered heat practi- 
cally latent and caused intense chilling of the gas, 
already at very low temperature, and might produce 
liquefaction of the hydrogen. The experiments of 
Cailletet confirm strongly this view of Pictet’s expe- 
riment. But we know that no hydrogen was lique- 
fied in volume in the tube before it was opened. » 

Ten years later Olszewski tried to throw some doubt 
on the method followed in the hydrogen experiment 
of Pictet. He published in the Phzlosophical Magazine 
for February, 1895, a long article giving a full ac- 
count of his work of bygone years, in which he, with 
Wroblewski, produced liquefied gases. This article 
is a statement of Prof. Olszewski’s part in liquefying 
gases and air. In the course of the article he criti- 
cises Pictet’s hydrogen experiment, saying that 
hydrogen made as Pictet made it would be contam- 
inated with water and carbon dioxide. 

As a piston works in a pump cylinder, what is 
termed clearance occurs. This is the failure of the 
piston to expel everything from the cylinder. It is 


166 LIQUID AIR AND THE 


mechanically impossible to do this with steel or iron 
parts, as the piston cannot well be so accurately 
made as to just touch the cylinder on its completion 
of a stroke. Even if it could, the valve passages 
would be left. 

As all gases are elastic by nature, it follows that, 
when a pump is caused to operate upon a gas, the 
clearance of the piston is a great obstacle to its 
operation. As the-piston of a pump cannot abso- 
lutely touch the cylinder end at each stroke, some 
gas must always remain in the cylinder, and during 
certain conditions of tension and compression, when 
the suction is of high degree, and the delivery is 
against a high pressure, the piston may work back 
and forth without any result whatever. The gas re- 
maining in the cylinder ends may be enough in 
amount to prevent any movement of the suction or 
inlet valve, or to admit other gas if it were opened, 
and not enough, on the other hand, to open the outlet 
valve, or, if it were opened, to go through it. 

This difficulty, inherent in all ordinary piston air 
pumps, Pictet avoided by coupling his pumps two in 
a set. Thus, when one pump was aspirating from the 
cooler jacket or other source of gas, it was deliver- 
ing, not against a high pressure, but into the suction 
pipe of the other pump. The other pump took this 
partly compressed gas through its suction pipe as 
delivered by the first and gave it its second compres- 
sion. 

By thisarrangement the difficulties were suppressed 
and the four pumps working in sets of two each 
operated perfectly. They were driven by band 

wheels at from 80 to 100 revolutions per minute. 


LIQUEFACTION OF GASES. 167 


The temperature was determined by a formula 
which is deduced from the mechanical theory of 
heat applied to change of state. The formula can 
be found in the paper of Prof. Pictet-as given in the 
Annales de Chimte et de Physique, Paris, fifth series, 
vol. xiii., or in the Archives des Sciences Physiques et 
Naturelles, Geneva, January 15, 1878. 

It is most interesting in this paper, which is the 
definite and authoritative presentation of the experi- 
menter’s views to find the following passage. It must 
be remembered that the oxygen had been liquefied 
in an opaque tube, that it was withdrawn therefrom 
by the cock under enormous pressure, and that the 
' sight of the jet, which lasted only three or four 
seconds, was the nearest approach to really seeing 
liquid oxygen which the definite experiment afford- 
ed. We quote the passage: 

“ We must try to render this liquid oxygen vwestble 
by condensing it in transparent apparatus. The pro- 
blem is very complex, bristling with practical diff- 
culties. We must avoid the condensed ice (gzvre, 
hoar frost) which instantly forms on cold surfaces, 
and impairs visibility; we must have tight joints with 
fragile material,” etc. 

Had Pictet foreseen the importance of the spher- 
oidal state in its relations to the handling of liquefied 
gases, and could he have divined how greatly it 
would facilitate all operations with them, he would 
_have seen the difficulty disappear in great part. But 
no human being could have imagined how greatly 
the maintenance of the spheroidal state was to affect 
the question. 

The same desire to get oxygen in quantity is here 


168 LIQUID AIR AND THE 


discernible which formed the inspiration for Wrob- 
lewski, Olszewski and Dewar. A scientist might be 
satisfied with Cailletet’s mist or with Pictet’s jet, but 
they were not. The desire to see oxygen and the 
other gases liquefied in volume has proved itself no 
mere idle dream, but a real, earnest and scientific 
longing. The effort and desire to satisfy this long- 
ing has led to the achievements commemorated in 
this volume. 

The oxygen in five of Pictet’s early experiments 
was evolved from a mixture of 700 grammes potas- 
sium chlorate and 3co grammes potassium chloride. 
This mixture may be taken as a typical one. 

The hydrogen mixture used in his experiment of 
January 10, 1878, consisted of potassium formiate, 
i261 grammes; potassium hydrate, 500 grammes. 

*The importance and value of Pictet’s early work 

cannot be overestimated. His double cycle with 
continuous liquefaction of the gases in the two re- 
frigerating cycles has been the instrument of the 
greatest successes in the hands of subsequent work- 
ers. All who worked upon this line in those early 
days overestimated the importance of pressure, but 
the keynote of Pictet’s work was a very advanced 
refrigerating apparatus. The critical temperature — 
is the great element in attaining success in liquefac- 
tions. It would have been but a small change to 
have compressed by mechanical means the gas to be 
liquefied. Had he done so, the effect would have 
been twofold. 

He would have had more gas to be acted on. As 
his experiments were conducted, he had a very 
limited supply of gas, and on opening the cock of 


LIQUEFACTION OF GASES. 169 


his apparatus it rushed out violently, and a fleeting 
glance of a second or two at the liquefied gas wasall 
that it was in his power to obtain. But had he gone 
a single step further, and connected a third pair of 
pumps to the inner tube, J7, of the gas condenser, 
there is every probability that he would have suc- 
ceeded.in his long-cherished wish much better. To 
him might have been granted the success claimed 
by Olszewski, of pouring for the first time liquefied 
oxygen or air from one vessel into another. But the 
work of Natterer and Andrews had its effect, and 
high pressure was striven for, and static air and 
oxygen remained for several years an unfulfilled 
hope and expectation. 

Pictet, in the year 1885, devotes .a paper to a new 
refrigerant, which has been named from him the 
liquide Pictet. \t is still used by him for the pro- 
duction of low temperatures. The paper will be 
found in the Comptcs Rendus, vol.c. He suggests 
that, for the production of low temperatures, a mix- 
ture of two or more volatile liquids may be em- 
ployed. It has been aptly said that in mixing 
metals so.as to produce new alloys the metallurgist 
is able to produce so many new metals. Each alloy 
may be taken as equivalent to a new metal. The pro- 
pertics of an alloy are not the average of the proper- 
ties of its constituents. In specific gravity, electrical 
conductivity, thermal and other properties no aver- 
age can be traced in many instances. 

Pictet found that the case was the same with mix- 
tures of liquefied gascs, and in the paper in question 
discusses at some length the use of such liquids, 
which at relatively low temperatures separate into 


170 LIQUID AIR AND THE 


their components. He gives a table of the boiling 
points of different mixtures of carbon dioxide and 
sulphurous oxide, using molecular mixtures, or mix- 
tures in which the proportions of the constituents 
stand in molecular proportion to each other. 

He succeeded in producing liquids which boil any- 
where from —71° C. (—95° F.) to —7°5° C. (—18'5 F.) 
But this range of selection open to the physicist is 
not the only advantage. There is a sort of recupera- 
tive or self-intensive action involved which makes the 
liquide Pictet peculiarly available. 

At low pressures its evaporative power is .aug- 
mented by its disposition to dissociate molecularly, 
_or to separate into the two gases, carbon dioxide and 
sulphurous oxide. At high pressures a sort of chem- 
ical affinity of low order seems to come into play, and 
the two gases liquefy much more easily than they do 
when unmixed. It is easy to see how this phenome- 
non lightens the work of the pump used to condense 
them. On the exhaust side the action is aided by 
the dissociation tendency of the liquids evinced in 
their gasification. This lightens the work of the 
pump, as it does not have to draw so hard to cause 
rapid evaporation. This evaporation is the refrige- 
rating action. 

At high pressures the chemical affinity also helps 
the work of the pump; for, less power being required 
to liquefy them than otherwise, the pump has not got 
to develop the same pressure as it would otherwise. 
Hence its work is lightened on the pressure side also. 

This peculiarity is brought out by a comparison 
of the “guide Pictet (formula CSQO,) with sulphur- 
ous oxide. At high temperatures the vapor ten- 


LIQUEFACTION OF. GASES. 171 


sion of the “guide Pictet is higher than that of the 
sulphurous oxide. But on increasing the pressure 
and lowering the temperature the vapor tension in- 
creases in a less rapid ratio with the /éguzde Pictet than 
with the sulphurous oxide, and at a low enough 
point. the sulphurous oxide shows the higher tension. 
In graphic terms the curves of tension and tempera- 
ture relations cross each other. 

All of Pictet’s work cannot be given within the 
limits of this book. This chapter gives the summary 
of his original liquefaction of gases. But his prac- 
tical mind sought fields for the utilization of his dis- 
coveries, and in subsequent chapters will be found 
described his application of low temperatures to 
treatment of disease and to the purification and pro- 
duction of chemical and technical products. 


LIQUEFACTION OF GASES. 173 


GLEARA BRAK: 
BOUISS PAUL GC AICLE TET: 


The life of L.-P. Cailletet—His education—Honors received— 
His modification of Colladon’s apparatus—Accidental 
liquefaction of acetylene by release—Description of his 
apparatus—How the apparatus was filled—The full ap- 
paratus with hydraulic press—Liquefactions of nitrogen 
oxide—Of carbon monoxide and oxygen mixed—Lique- 
factions of the same separately—-His letter of December 2, 
1877, to the French Academy—Liquefaction of nitrogen 
——Of hydrogen—Rival claims of Cailletet and Pictet -— 
Mercury stopper method—Manometers—-Original meth- 
ods of testing—Eiffel Tower manometer—Carbon dioxide 
experiments—Mercury pump—High pressure gas reser- 
voir—Ethylene as a refrigerant—Closed cycle method— 
Accelerated evaporation—Electric conductivity at low 
temperatures—Comparison of thermometric methods—La 
Tour’s experiment repeated. 


~ Louis-Paul Cailletet was born in ChAatillon-sur- 
Seine, in the Céte d’Or, France, on September 21, 
1842. He studied at the Lycée Henri IV. and then 
entered the Ecole des Mines, Paris. On finishing his 
course he returned to Chatillon-sur-Seine and soon 
was placed in charge of his father’s iron works at 
that place. ; 

-He made many researches into the working of 
blast furnaces, the problems of combustion and of 
metallurgy. The occlusion of gases and the causes 
of explosion of iron while in the process of forging 


174 LIQUID AIR AND THE 


were also investigated, and a number of his papers 
were published in different scientific journals. 

His investigations in the field of the compression 
and liquefaction of gases began about 1876, and 
reached their culmination in his liquefaction of oxy- 
gen and other “ permanent gases” in 1877 and 1878. 
But he did not desert the subject, and for years after 
numerous papers by him in the Comptes Rendus attest 
his interest in it and his indefatigable powers of 
work. . 

Honors were given him for his work, of which we 
do not give the full list. It must suffice to say that 
he was elected a correspondant of the French 
Academy of Sciences December 17, 1877. On April 
28, 1884, he received the prix Lacarze from the 
French Academy of Sciences, for the liquefaction of 
gases, the report coming from the following dis- 
tinguished committee: Profs. Chevreul, Fremy, 
Wurtz, Cahours, Friedel, Berthelot, Dumas, Pasteur 
and Debray; and on May 26, 1884, he was elected 
membre libre of the Academy. 

He had done much work upon the other subjects 
when he took up the action of gases under compres- 
sion. At first he had no idea of liquefying the per- 
manent gases, but he was a keen observer, and this 
led to his success. 

Looking back at the work of his predecessors, he 
found that they had settled upon one type of com- 
pression apparatus, which rendered possible the sub- 
jection of a considerable body of gas to an enormous 
pressure, and that in a transparent tube. 

He had adopted Colladon’s well known compres- 
sion apparatus (page 136) for the purpose of his inves- 


LIQUEFACTION OF GASES. 175 


tigations, but he connected to the hydraulic press by 
which it was operated a valve for sudden release of 
the compressed gas from pressure. 

He builded better than he knew. His release 
method introduced a factor which produced intense 
cold in the gas, which cold brought about its lique- 
faction. The importance of the critical temperature 
may have been perfectly well known in 1877, but it 
was not so fully appreciated as now. Cailletet, 
almost by accident, came upon a method which 
enabled him to liquefy gases, simply because it low- 
ered their temperature below the critical point. 
But when Cailletet first lowered the temperature in 
this way he did it without the least idea of liquefying 
agas. The liquefaction was accidental, and was not 
even recognized as being what it was. 

The authoritative statements of each step of Cail- 
letet’s work, published as soon as each step was com- 
pleted, are given in the Comptes Rendus of the French 
Academy. He follows the custom of some other 
Scientists by giving in another publication the résumé 
of his entire work up to the time when it was prac- 
tically complete. <A paper by him, with illustrations 
of his apparatus, is published in the Axnales de 
Chimte et de Physique, 1878, which does this for his 
_ first work on the liquefaction of gases. 

Pictet follows a like course, publishing specific 
papers in the Comptes Rendus, and following them 
with a general illustrated description in other publi- 
cations. . 

The work of Cailletet on the liquefaction of gases 
begins with his work on acetylene. From the some- 
what concise statements in the Comptes Rendus we 


170 LIQUID AIR AND THE 


may trace his work as originally published. But it 
will be better to invert the natural order a little and 
first present the more general view of his operations 
with the description of his apparatus, and then give 
a brief recapitulation of the more important Comptes 
Rendus articles. 

Cailletet’s original liquefactions seem to have been 
less satisfactory than Pictet’s, as the proof uepended 
on the production of a mist or fog of the liquefied 
gas. He compressed the gas which he was working 
on, cooled it, and then suddenly released it from pres- 
sure. The quick expansion absorbed heat, the tem- 
perature fell and he got the mist, which he describes 
by the word érouillard. We find here an indirect 
appeal to the criticaltemperature. He refrigerated 
the gas to such an extent by the sudden expansion 
that it fell far below the critical temperature. 

The experiments were easily performed, and could 
be repeated over and over again upon the same por- 
tion of gas during the same day, so as to acquire force 
by reiterated success. The apparatus and its use 
were both simple, relatively speaking, and as demon- 
strations the experiments were accepted by scien- 
tists of absolutely the highest standing as satisfac- 
tory. 

The compression apparatus will be recognized as 
a development of Colladon’s and of Andrews’ appa- 
ratus, which is illustrated and described elsewhere 
(pages 136and 147). The cut shows the essential por- 
tion of Cailletet’s apparatus as given by him in his 
article in the Annales de Chimie et de Physique of 
1878, in which journal he describes his work in 
more detail, or, at least, in more popular style than 


LIQUEFACTION OF GASES. 177 


in the Comptes Rendus. In the latter publication, 
under various dates, are published the somewhat 
condensed statements of the results of his work, but 
in the Annales a general view of the course of ex- 
perimentation which led up to his final liquetactions 
of 1877 is given. 

Referring to the cut, B represents a heavy steel 
cistern into which a glass vessel, 7, dips, whose upper 
end forms a tube, 7P. Thisis 
sealed at the top, P, and contains 
the perfectly dry and pure gas. 
It is sealed with an absolutely 
tight joint where it passes 
through the metal piece, A. A 
gland, 4, screws down against 
the flange on the bottom of 4, 
squeezing it against the packing 
shown under A. JJ is an open 
glass vessel which contains a 
cooling mixture if such is desired 
to be used, and a glass shade, C, 
covers the upper part simply as 
amatter of security. The darkly 
shaded part within B and J re- 
presents mercury; the lighter 
shaded portion in Bis water. A 
cock serves to draw to draw off 
the refrigerating agent from J. 
Uis a pipe joined by the coup- 
ling, R £,to the mercury vessel. S is the platform 
which supports the shade, C, and refrigerant ves- 
sel, M. 

When the apparatus is first set up, the level of the 


tion Apparatus. 


178 LIQUID AIR AND THE 


mercury in Z is much lower than is shown in the 
cut. It would be considerably below 7, or not far 
from the bottom of the gas tube. 

By a pump or hydraulic press water is forced into 
B. This forces the mercury up into the tube, P7, 
until the gas is greatly compressed. The upper 
portion of the gas tube, it will be seen from the con- 
struction, is the only part which is subjected to a 
bursting pressure, and it is so small in diameter that 
it can be made very strong without being of inordi- 
nate thickness. 

The gas was compressed by a hydraulic press, as 
shown in the cut, page 180. A valve in the compress- 
ing press or pump was suddenly opened by the han- 
dle, O, and the gas was so cooled by its own expansion 
that a mist formed, which was composed of particles 
of the liquefied gas. The liquefaction consisted in 
the production of this mist. 

In his original work Cailletet used a very power- 
ful screw press worked by handles on a large fly- 
wheel. In the illustration of the entire apparatus the 
disproportion between the great compressing press 
and the little glass tube holding its minute quantity 
of gas is impressive. 

The filling of the gas tube with dry gas was thus 
effected. The upper end of the tube was left open. 
A drop of mercury was placed in the large gas tube 
or bulb, the tube being held horizontally, and a tube 
from the gas evolution apparatus was slipped over 
the other end. A current of gas to be experimented 
on, purified by proper chemicals, was passed through 
the tube, and while it was still passing the upper end, 
P, was sealed tight with the blowpipe or blast-lamp. — 


LIQUEFACTION OF GASES. i79 


This was done with the tube in an approximately 
horizontal position. Next the tube was returned 
“into the vertical position with the sealed end upper- 
most. The drop of mercury ran down into the bent- 
up lower end, and the gas was thus hermetically 
sealed in the tube. It was then lowered into the 
reservoir of mercury, 8. The connections were made 
and all was ready for the experiment. 

The gas tube, it will be observed, differed from 
Colladon’s in its bent-up lower end. This feature 
enabled the globule of mercury to act as a valve and 
seal the gas up in the tube before the latter was in- 
serted in the cistern. 

It is impressive to contrast the diminutive size of 
the liquefaction apparatus with that of the hydraulic 
press. The whole mechanism, whose size can be 
judged from the figure of the operative, is devoted 
to producing liquefaction phenomena in a glass tube 
of a fraction of an inch in internal diameter. The 
old error was perpetrated of overestimating the 
importance of pressure and underestimating the 
influence of reduction of temperature. 

The first cloud he ever produced with a gas in his 
apparatus was with acetylene on sudden release 
from pressure, and it was unintentionally produced. 
He was experimenting with the gas, subjecting it to 
pressure not sufficient to liquefy it. He opened his 
release cock, and, as the gas expanded suddenly, he 
saw a mist or cloud form within the gas tube. 

The first stroke of the piston of an air pump in ex- 
hausting a glass receiver produces such a cloud 
within the receiver, owing to the precipitation of 
moisture in the air by the cold due to rarefaction of 


LIQUID2 AIR AND TALE 


180 


LIQUEFACTION OF GASES. 181 


the air in the receiver. The appearance is very 
familiar to all who have used the old-fashioned air 
pump. It was, therefore, quite natural for Cailletet 
to conclude that the acetylene with which he was 
working was impure. He wished to avoid the pres- 
ence of impurities. So he procured some absolutely 
pure acetylene gas from Berthelot’s laboratory, filled 
his tube with it, and on compression and sudden re- 
lease got the same cloud as before. He tried nitro- 
gen dioxide and again the cloud appeared. 

He now recognized fully what was occurring, and 
saw a very simple and effective way of showing the 
liquefaction of. gases. He tried his famous experi- 
ment of December 2, 1877, in which he used oxygen 
gas and got the same appearance of a mist with it. 

The large illustration shows the full apparatus 
used by Cailletet. 4 is a steel cylinder with plunger 
actuated by a screw, /, and held in brackets, B Z. 
M is a wheel by which the screw is turned. The 
cylinder is filled with water by the glass funnel, G. 
To relieve the pressure when it might be desirable, 
a special valve operated by a wheel, O, was provided, 
and it was this valve which constituted the distin- 
guishing feature of Cailletet’s process and apparatus. 

At S is a cross-connection to bring into connection 
the hydraulic cylinder, 4, the liquefaction apparatus 
of page 177, and the gauges. Two of these are shown. 
One, designated by WV, is a Thomasset manometer ; 
WN’ is a Cailletet glass bulb manometer, such as 
spoken of on page 187. 

The liquefaction apparatus, #, stands upon a shelf 
of iron, 4, with set screws, d d, to secure ae mercury 
reservoir, a, 


182 LIQUID AIR AND-THE 


The value of his work depended on the sudden 
release of the gas from pressure. As this was 
effected by opening a valve on the compressing ap- 
paratus, it caused the mercury to suddenly fall in 
the gas tube, but there was no loss of gas. The 
same sample of gas could be experimented with 
over and over again. 

The sudden release, Cailletet calculates by Pois- 
son’s formuia, should give a lowering of tempera- 
ture of 200° C. (360° F.) This release constitutes 
the advance in his work over all his predecessors. 
Asa physical demonstration, it gives a very elegant 
method of cooling a gas below its critical tempera- 
ture. It is so direct an attack upon the molecules, 
and is so quick, as to effect the refrigeration without 
need of jacketing the tube. The expansion is almost 
perfectly adiabatic. 

The pressure applied to the gas was determined 
by various manometers. One of his own devising, 
which we describe from papers in the Comptes Rendus, 
was employed, as well as another one by Thomasset. 
Both were connected to his compressing press. For 
lower pressures he could use an open end manome- 
ter of his own construction. This, however, was 
more adapted for standardizing purposes; his glass 
compression manometer was the instrument best 
adapted for use on his gas liquefying appara- 
tus. 3 | 

In the Comptes Rendus of October 29, 1877, page 
851, he describes his work with acetylene. At 18° C. 
(64°4° F.), and a pressure of 83 atmospheres, he got 
drops of liquid acetylene. Then, on suddenly releas- 
ing it from pressure, a fog or cloud of acetylene 


LIQUEFACTION OF GASES. 183 


formed. He reports the liquid as colorless, mobile 
and of a high refracting power. 

A letter from him is given in the Comptes Rendus 
for November, 1877, page 1017,1n which he says that 
he has liquefied nitrogen dioxide, using a tempera. 
ture of —11° C. (12°2° F.)and a pressure of 104 atmo- 
spheres. At 18° C. (64'4°F.) it resisted a compres- 
sion due to 270 atmospheres. Formene was tried, 
and on release gave a mist. 

Next, in the same volume, he says he got a mist 
with a mixture of carbon monoxide and oxygen, and 
we find in the same volume, page 1217, his letter 
to the French Academy of Sciences, announcing the 
liquefaction of oxygen and carbon monoxide. It is 
dated December 2, 1877, and is given below. The 
very modest tone of the letter, and the feeling of 
the writer that his mist of condensed gas was hard- 
ly a sufficient liquefaction, are very evident, and 
inspire the readers of the letter with additional con- 
fidence in Cailletet’s work. 

‘The letter is historic, as it is used to determine the 
question of priority between the French and the 
Swiss scientists, Cailletet and Pictet. 

We give a translation of the letter : 

“T hasten to tell you, you first, and without losing 
a moment, that I have liquefied to-day both carbon 
monoxide and oxygen. 

“T am, perhaps, wrong in saying liquefied, for at 
the temperature obtained by the evaporation of sul- 
phurous acid, say —29° and 200 atmospheres, | do 
not see the liquid, but a mist so dense that I can 
infer the presence of a vapor very near to its point 
of liquefaction. 


184 LIQUID: AIR AND PHE 


‘“‘T write to-day to M. Deleuil to ask of him some 
nitrogen protoxide, with the aid of which I will be 
able, doubtless, to see carbon monoxide and oxygen 
flow. 3 

“P.S.—I have just performed an experiment 
which gives my mind great peace. I have com- 
pressed some hydrogen to 300 atmospheres, and, 
after cooling to —28°, I have released it suddenly. 
There was no trace of mist in the tube. My gases 
(CO and O) are then on the point of liquefying, this 
mist not being produced except with the vapors near 
liquefaction. The (frévzstons) prophecies of M. 
Berthelot are completely realized. 

| ‘ LOUIS _ CAIEEET Eas 

-~December27 1377.5 

The control experiment with hydrogen, with its 
negative results, gives great conclusiveness to the 
experiments in which a positive result was obtained. 

The letter had been deposited, sealed, with the 
Academy of Sciences at Paris on December 3, 1877. 

He next turned his attention to nitrogen, com- 
pressed it to 200 atmospheres at 13° C. (55°4° F.), and’ 
on releasing it from pressure it condensed very per- 
fectly, “like’a pulverized liquid,” giving ‘“ droplets 
of appreciable size,” which gradually disappeared 
from the walls toward the center of the tube, form- 
ing finally a vertical column around the axis of the 
tube. The duration of the phenomena was about three 
seconds. On December 30, 1877, the experiment 
was repeated many times before several members of 
the Academy. | 

-The next day he tried to liquefy hydrogen in pres- 
ence of MM. Berthelot, Sainte-Claire Deville and 


LIQUEFACTION OF GASES. 185 


Mascart, obtaining evidences of the liquefaction of 
the gas, and repeating the experiment a great many 
times. He compressed it to 280 atmospheres, and, 
on sudden release, it formed an exceedingly fine and 
subtile mist which suddenly disappeared. 

Air purified from carbon dioxide and from water 
produced the mist without difficulty. 

Berthelot, in commenting on the liquefaction of 
hydrogen, says: 

“The extreme tenuity of the liquefied particles 
which form this mist of hydrogen, a sort of dissem- 
inated glimmer (/weur),as well as their more rapid 
return to the gaseous state, are in perfect accord 
with the comparative properties of hydrogen and of 
the other gases.” (Comptes Rendus, vol. |xxxv.) 

The rival claims of Pictet and Cailletet are com- 
pared by Sainte-Claire Deville, who says that Caille- 
tet’s experiments were repeated in the Ecole Normale 
on December 16, and succeeded perfectly. This 
was the day of his election as a correspondent of the 
French Academy of Science. The priority of dis- 
covery is awarded to Cailletet. 

When we see later how much store Olszewski 
sets by his claim to have been the first to produce 
liquefied oxygen in quantity sufficient to be poured 
from one vessel to another, when we read between 
the lines of Cailletet’s letter that he would have 
liked to produce a real visible bulk of liquid 
oxygen, we can appreciate Pictet’s work at its full 
value, and feel that the two deserved at least equal 
honor. | . 

The two worked quite independently and without 
knowledge of the scope of each other’s work. It 


186. LIQUID AIR AND: THE 


seems a pity that they could not have been associated 
as were Wroblewski and Olszewski five years later. 
It is the great chemist Dumas who, in the 7ransac- 
tions of the Academy of Science, calls attention to 
their ignorance of each other’s work. It is pleasing 
to know that later in life they contracted an inti- 
mate friendship with each other.. 

Cailletet seemed to think that, as he had liquefied 
the constituents of air, the liquefaction of air itself 
was of little importance. 

On trying air at 200 atmospheres, and on 1 cooling 

the. upper part of the tube with nitrous oxide, 
threads of liquid appeared on the walls of the tube. 
They were very agitated, and, on running down until 
they struck the mercury, they recoiled or drew 
back. 
He felt that a control experiment. was ved to 
determine if a liquid near its point of condensation 
would act in this way. Ether was selected on account 
of its high volatility. He poured it downa tube and 
found that it gave the same effect as he had seen in 
his aemaeesler apparatus. 

Inspired by confidence from this control test, he 
increased the degree of compression in his apparatus 
until the mercury rose into the small tube within 
the refrigerating. vessel, the pressure rising -to 225 
atmospheres. and the liquid threads or streamlets in- 
creasing 1n number. 

Continuing the compression until 310 atiehheees 
pressure was attained, the mercury reached the level 
of the nitrous oxide, when it froze, stopping up the > 
tube. The refrigerating apparatus was at-once re- 
moved, when it was seen that the surface of the 


LIQUEFACTION OF GASES. 187 


frozen mercury was covered with hoar frost, which 
he thought was solid air. 

This closing the tube with a stopper (douchon) of 
frozen mercury appears to him a method of very 
useful application in some of these investigations. 

Cailletet showed much ingenuity in his methods, 
and the construction of his manometer for indicating 
high pressures and its standardization ee a EpCg 
sample of his work. 

He first determined that glass yielded to pressure 
and returned perfectly to its original-shape. He 
then constructed a manometer or pressure indicator 
by making what was practically a mercurial ther- 
mometer. The bulb was hermetically sealed in -a 
steel reservoir full of water. .On pressure being ap- 
plied to the water, the bulb was-squeezed and the 
mercury rose. Thesteel reservoir could be connected 
by a pipe to any fluid whose pressure was to be 
tested, as, for instance, to the water or mercury in 
his hquefaction apparatus. The manometer was kept 
ata uniform temperature by meltingice. The height 
to which the mercury rose gave the pressure. 

The methods he adopted for testing its: accuracy 
are striking. He fitted it with an ‘ades like a maxi- 
mum thermometer and lowered it to known depths 
in the sea, in the harbor of Toulon, so that the water. 
produced the known pressure for its calibration. He 
complains of the bad seas encountered. Another 
way was to lower it into an artesian well. In these 
cases he introduced maximum and minimum ther- 
mometers with it in order to secure corrections for 
temperature. — we ; 

He also constructed an open end mercurial mano-: 


188 LIQUID AIR AND THE 


meter, which wasa long tube running up a cliff, 
and by maintaining mercury in it at different heights 
he produced a range of pressures from zero up to 
34 atmospheres. This he used as a standard for test- 
ing the accuracy of his small manometers. 

This was in the early period of his labors. It was 
not likely that such a practical and hard working 
scientific investigator could fail to see years later the 
chance which the Eiffel Tower, nearly a thousand 
feet high, offered for the construction of an open 
tube manometer. He interested M. Eiffel in the 
work. A soft steel tube was erected which ran up 
the framework of the tower. It was 4% mm. (nearly 
4 inch) in internal diameter. Every 3 meters (nearly 
10 feet) a projecting pipe with stopcock was placed, 
and to each of these a glass tube, in length slightly 
in excess of the 3 meters, was placed. Thus read- 
ings could be taken all the way up the tube. As 
each glass tube became filled, and the readings com- 
prised within its length were completed, the stop- 
cock was closed and more mercury was PHM ES in 
at the bottom. 

The mercury came in from below. The steel tube 
dipped into a cistern, and a pump by hydraulic pres- 
sure forced the mercury into the cistern and up into 
the tube. 

With this apparatus some 400 atmospheres of 
pressure could be reached. 

Some rather curious corrections had to be applied. 
For a range of temperature of 30° C. (54° F.) the 
tower and steel tube expanded 3,5, of their length 
or height. This was a very minor matter. But 
the mercury for the same range expanded y1,;. The 


LIQUEFACTION OF GASES. 189 


heat expansion of the mercury, therefore, had to be 
corrected. The compressibility of the inercury and 
the diminished pressure of the air due to the great 
height were sufficient in extent to require correction 
also. 

He tried manometers, as we have seen, by lower- 
ing them into water of great depths. The mano- 
meters operated by mercury rising in a glass tube. 
In the artesian well or in the harbor of Toulon the 
manometer was inaccessible, and an index was 
needed to show how far the mercury had risen in 
the tube. : 

This he secured by gilding the interior of the 
glass tube. As the mercury rose, it amalgamated 
with the gold and removed it from the glass. The 
portion of the glass tube stripped of gold showed 
how much of the tube had been filled with mercury, 
The arrangement operated like a maximum ther- 
mometer. 

It cannot but impress the reader of the old time 
original papers on scientific work which have 
marked the steps of our progress that there is much 
good matter in them which has been forgotten. An 
original memoir ten years old is apt to be forgotten 
or to be treated as something which has been sup- 
planted by more modern writings. But this view of 
the case is wrong and unjust, for the history and 
development of science is a most interesting study, 
and in these days, when the inductive method of 
teaching is so extensively employed, the old original 
papers by the great ones of the scientific world 
should receive much more attention than is generally 
awarded them. This book has been written from 


190 STIOUIDFAIR GAN Dearie 


this standpoint. The bibliography of liquid air and 
liquefied gases testifies to the amount of material 
there is to be drawn upon. 

Cailletet’s work on his manometers shows a very 
good and conclusive method of measuring high pres- 
sures. His operations indicate an original cast of 
thought. After his great work on the liquefaction 
of oxygen by the use of his happily utilized pressure 
release he continued his work on gases. In 1880 he 
investigated the phenomena brought about by com- 
pressing a mixture of carbon dioxide and air. He 
found that the carbon dioxide was first liquefied and 
then disappeared as the pressure rose, which he in- 
terpreted as the solution of aliquid ina gas. It 
reminds us of the solution of a solid in a gas shown 
when a solution of a solidin a liquid is heated: to a 
point above the critical one for the solution in ques- 
tion. Thus,if potassium iodide or chlorophy]l is dis- 
solved in alcohol, and the solution is heated in a sealed 
tube to 350° C. (662° F.), the whole disappears, and 
the solid is,so to say, dissolved or diffused in the gas- 
eous alcohol. The observation is-due to Bano 
and Hogarth, page 23. _ 

Guilletet noted the same thing with le liquid car- 
-bon dioxide and the gaseous air. He wished. to have 
some test to determine when his carbon dioxide 
parted from the liquid state, and he sought a coloring 
agent for it: He thought that, if he colored it, the 
change from liquid to gaseous would be discernible. 
After some trials of different agents, he found a 
coloring matter which would <dissolve in and. color 
liquid carbon dioxide. It was the blue oil of. gal- 
banum. 


LIQUEFACTION OF GASES. 191 


Galbanum is a resin imported from the Levant, 
used in medicine, and of somewhat uncertain origin. 
Those who are interested in the archzology of sci- 
ence will find it mentioned in Exodus xxx. 34. The 
old name for it was chelbenah. 

This ancient member of the pharmacopceia gave 
Cailletet the coloring matter he sought for. Liquid 
carbon dioxide dissolved it, and was colored blue 
thereby. On gasification the blue oil was deposited 
on the sides of the tube and on the surface of the 
mercury. 

He investigated the Seeuliar striations which 
occur around the critical point, and concluded from 
the action of the coloring matter that they were 
liquid carbon dioxide. The disappearance of the 
meniscus was determined to be due not to liquefac- 
tion of the entire contents of the tube, but to gasifica- 
tion. The general phenomena presented by a mix- 
ture of carbon dioxide and air when highly com- 

‘pressed were studied, and the results are given in 
the Comptes Rendus, vol: xc. 
Years later he returns to this aleston of coloring 
liquid carbon dioxide in order to determine the point 
of its gasification when heated in a sealed tube under 
pressure. He expresses some discontent with oil of 
-galbanum and tries iodine. He sublimes this in his 
gas tube, so that portions of the glass collect a subli- 
-mate. He liquefies carbon dioxide in this tube, when 
it becomes colored by the iodine. On heating to dis- 
appearance of the meniscus, he finds that.the gas or 
liquid in the lower part of the tube is blue, while that 
above is colorless, although iodine is there to.color it. 

_A test with the spectroscope shows that the car- 


192 LIQUID’ AIR AND THE 


bon dioxide colored with iodine gives the spectrum 
of iodine in solution, not of gaseous iodine. So the 
conclusion is reached that the disappearance of the 
meniscus is not necessarily synchronous with the 
attainment of the critical temperature. 

To further examine the question, he tries an analo- 
gous experiment with two liquids, immiscible under 
ordinary conditions. Amylic alcohol and common 
alcohol, each with some water, lie one above another 
without mixing. He places the two in a sealed tube 
and applies heat. The line of separation between 
them begins to disappear, vanishes, and striations, 
such as seen with liquid and gaseous carbon dioxide 
heated to the critical temperature, appear. 

He gives a new definition of the critical tempera- 
ture, as follows: The temperature at which a liquid 
anda gas above it are capable of mutually dissolving 
each other in all proportions. 

His condensing pump, without harmful clearance 
or lost space (saus espace nutstble), excited considera- 
ble attention. If acondensing pump has much clear- 
ance, if the piston or plunger does not go against the 
end of the cylinder as it expels the gas, as the pres- 
sure against which the pump works rises sufficiently 
high, no gas will be expelled, and the pump will do 
no work. This point is spoken of where Pictet’s ex- 
periments are treated of, on page 166, and his way of 
getting over the difficulty, the coupling of two 
pumps, was spoken of. 

Cailletet constructed a single acting plunger pump. 
It was placed with its cylinder vertical. The gas 
was forced out of its upperend. To avoid clearance 
he placed a quantity of mercury over the piston. As 


LIQUEFACTION OF GASES. 193 


it rose, the mercury was forced into the clearance 
space, so as to completely fill it and thus suppress its 
injurious action. 

It is evident that it is impossible to construct a 
pump without any clearance as they are ordinarily 
built. But the lquid piston obviates the trouble, 
and at each stroke every particle of gas is expelled, 
whatever may be the pressure against which it 
works. | 

Before Cailletet’s pump was devised, Regnault had 
experimented with a mercury pump on somewhat 
the same principle. The Cailletet pump has, how- 
ever, been accepted as a most valuable contribution 
to compressed gas work, and has been adopted by 
the Leyden University in its cryogenic laboratory. 
It has done much service in the hands of other 
investigators. 

ec icut ives alséction- of the, barrelolsthe 
pump. & Z#is the barrel with plunger, 4. The dark 
portion over the plunger is mercury. At a, 6 are 
packing rings of leather. R is the inlet valve, 
which is worked by a cam and lever system auto- 
matically. The neck, *O, through which the gas 
enters, can be connected by a rubber tube to the 
source of supply. S is an ebonite valve through 
which the gas is forced by the plunger into the bon- 
net which surmounts the barrel. The tube, 7 7, de- 
livers the compressed gas. A flexible copper pipe 
fjeconnected to ithe tube, 7 7, and leads to the 
vessel in which the gas is to be condensed. 

The operation of the pump is obvious. The 
plunger begins to rise, and the valve, &, closes. 
The plunger then drives the gas before it through 


194 LIQUID A 


IR AND THE 


the valve, S, and as it reaches the upper part of the 
cylinder, the mercury rising into the: narrow ‘tube 
below S expels the last traces of gas. As the 


Shy 


wy 


: 
§ 


Cailletet’s Mercury Plunger - 
Air Pump, — 


insure the tightness of th 


plunger descends, an almost 
perfect vacuum forms above 
the mercury until the valve, 
R, is passed and opens, so 
that the gas to be com- 
pressed can enter. On the 
return stroke, this quantity 
is driven out through the 
valve, S. 

If any mercury enters the 
bonnet or space above the 
valve, S, it cannot reach the 
gas reservoir, because the 
outlet tube, 7, takes the gas 
from the top of the space. 


~ The pump. was operated 


with a fly-wheel and crank 
motion, much like Natter- 


- er’s pump. Sometimes a 


screw valve was placed on 
the summit of the. bonnet 
to make possible the expul- 
sion of all air from the 


pump. acre | 
tihe> base cotethe zbarret 


“screwed into a socket or 


base piece, which held some 
glycerine ‘or. mercury, .to 
e packings, 2 and J. 


The presence of mercury made. the lubrication ~ 


LIQUEFACTION OF GASES. 195 


problem somewhat troublesome, as ordinary oils 
and grease coming in contact with the mercury 
formed almost solid compounds. Eventually Cail- 
letet adopted 
vaseline and 
glycerine as lu- 
bricants. 
Wath this 
pump a man, 
without over- 
exertion, readi- 
ly liquefied 
20. t.0: 5 0.0 
grammes of 
carbon dioxide 
in an hour. 
Recognizing 
the danger of 
the larger cyl- 
inders used for 
holding lique- 
Med oases, 
Cailletet re- 
placed them by 
a group of nine 
Bopper tubes, = 
arranged in a ~ 
Eylindrical.:. 9.7, 
group, and all Sates 


connected by ~ Cailletet’s High Pressure Reservoir 
for Liquefied Gases. 


small copper 
tubes, @ a, to one central delivery cock, V, and 
outlet coupling, O. The group was mounted on 


all 


196 LIQUID AIR AND THE 


trunnions, #,in a frame, as showninthe cut. The 
tubes had a capacity of about four liters. 

The mercury pump without lost space (sans 
espace nuisible), as invented by Cailletet after Reg- 
nault had experimented with one, is of special 
interest, and has been very often used in liquefied 
gas investigations. One of the most celebrated high 
pressure gas laboratories, that of the University of 
Leyden, uses it in a modified construction. The 
mercury no longer lies on the plunger, but is beneath 
its end. A U-shaped tube constitutes the pump bar- 
rel. In one limb the plunger works downward. 
The bend of the tube is filled with mercury, and the 
outlet for gas as compressed is at the top of the 
other limb. 

All through the history of investigations on this 
subject we find at intervals Cailletet’s pump men- 
tioned ; so it has survived a long time as things go in 
this age of progress. The new demand is for a pump 
that will continuously and powerfully compress a 
gas. Formerly it was a single sample of gas at a 
time which was to be compressed. This was effected 
by a screw or other device, as explained and de- 
scribed in many places in this book. But when Pic- 
tet, in 1877, established his double cycle liquefaction 
of gas, he instituted a method calling for a pump 
with constant delivery at high pressure, and his 
method has been utilized in some shape or form by 
most subsequent investigators until within the last 
few years. It is by no means abandoned yet, and 
Cailletet’s pump is still, in inproved form, doing ser- 
vice at the cryogenic laboratory of the University 
of Leyden. 


LIQUEFACTION OF GASES. IQ7 


Cailletet and Hauteville, in 1882, approached the 
difficult task of determining the specific gravity of 
liquid oxygen in the following way: 

One volume of oxygen was mixed with seven vol- 
umes of carbon dioxide. The mixture was submit- 
ted to pressure while maintained at a temperature 
exceeding the critical temperature of the relatively 
easily liquefied carbon dioxide. Then, after the com- 
pression was effected, the temperature of the mixture 
was lowered and the two gases liquefied together 
without separation. Numerous experiments with 
other gases had shown that there was no reason to 
expect any shrinking, except in very slight degree, 
upon mixing two such liquids. The specific gravity 
of liquid carbon dioxide was easily determinable and 
was accurately known. The mixture of liquid oxy- 
gen and carbon dioxide was perfectly manageable, 
and its specific gravity was determined with ease, 
and by simple alligation the following results were 
obtained. At the melting point of ice, 0° C. (32° F.) 
and at —23° C. (—9'4° F.), it was for various pres- 
sures expressed in atmospheres : 


Pressure. Soe ek cee) —23° C. (—9'4° F.) 
200 0°58 sp. gr. 0°84 Sp. gr. 
275 C05.) OS3e es 
300 O7Os O8Oul a 


As a control, a similar experiment with nitrous 
oxide, substituted for carbon dioxide, gave at 300 
atmospheres and at —23° C. (—g°4° F.) a specific 
gravity of 0-94. 

Another of Cailletet’s classic discoveries is the use 
of liquid ethylene as a cooling agent. According to 


198 . LIQUID AIR AND THE 


him, it liquefies at the following pressures and tem- 
peratures: 


As, atmospneres ataie-C.<(39°oegn) 


50 a3 66 4° Ce (Go -28 F.) 
56 “ “ 8° C. (464° F.) 
60 . EOS Ge tus O aecey 


Its critical temperature is about 13° C.(55°4° F.), 
while that of its predecessor in the refrigerating line, 
carbon dioxide, is 31° C. (87°8° F.) Using a carbon 
bisulphide thermometer, he reached a temperature 
of 105° C. (—157° F.) in liquid ethylene, while in 
liquid nitrous oxide he only reached —88° C. 
(—126'4°- F.) 

He made the ethylene by the old method: of. heat- 
iny together alcohol and concentrated sulphuric acid. 
The latter, with its high affinity for water, takes the 
elements of water from the alcohol, and gaseous cthy- 
lene is evolved. This gas he liquefied by the use of 
his mercurial pump just described. He found it far 
from manageable by his appliances, and’ first em- 
ployed it as a refrigerant in the form of a jet, remind-. 
ing us of Thilorier’s chalumeau de froid, or cold jet 
blowpipe, spoken of in a preceding part of this book 

(page 141). | 

In its release from confinement it goes into the 
gaseous State, not OMS HAs into snow, like carbon 
dioxide. 

The classic interest of this~ ieee lies in the 
great use that subsequent investigators have made 
of liquid ethylene as a refrigerant. Notably is this 
the case with the work done in the Royal Institution 
by Dewar. One of the most striking features of his. 


LIQUEFACTION OF GASES. 199 


work was the number of cylinders of liquid ethylene 
which he prepared for his liquefactions. Such was 
the comment made by Prof. George Barker on his 
visit to the Royal Institution. The quantity of 
liquid ethylene was as remarkable in its way as the 
liquefaction of air itself, and the manufacture of this 
ethylene was one of the principal sources of expense 
incurred in the Dewar liquefactions. 

The ease of liquefaction of ethylene, its reasonably 
high critical temperature and the highdegree of cold 
produced by its evaporation, make it a particularly 
valuable and manageable agent. The difficulties 
Cailletet experienced have disappeared with the im- 
_ proved appliances of fifteen years later. 

Ethylene is a very old acquaintance and a com- 
pound that, in giving its luminosity to coal gas, pee 
played an important role in technology. 

An objection to ethylene, as a refrigerating agent, 
is its cost. It is no great matter to make afew cubic 
feet of the gas from alcohol and sulphuric acid; 
but when it comes to condensing the gas to a liquid 
with many hundredfold reduction of volume, the 
cost becomes very great. A 5 or Io gallon cylinder 
of the liquid represents immense expenditure of 
alcohol. Cailletet’s very inartificial way of using 
ethylene as a cold jet blowpipe and letting the gas 
go completely to waste complicated the difficult gas 
liquefactions by the introduction of a very serious 
factor of expense. 

In a subsequent paper we see that he Bnirecisted 
this state of affairs and tried to work with léss waste 
and to introduce a rational economy into his. pro- 
cess. 


200 LIQUID AIR AND THE 


In 1883 Cailletet speaks of a continuous liquefy- 
ing apparatus, but declines to describe it. Hitherto 
he had operated with small quantities of liquid ethy- 
lene at atime, by the use of his mercury condens- 
ing pump, and had applied the ethylene as a jet, but 
now he uses a closed cycle. The ethylene circulates 
through a steel cylinder, being released from com- 
pression as it enters, so as to take the gaseous form, 
and reducing the temperature greatlv on the latent 
heat principle. Through the steel cylinder a tube 
passes, so that the two represent a condenser of the 
type of the well-known Liebig’s condenser, similar 
to Pictet’s apparatus. The pump draws out the gas 
from the cylinder and compresses it to the liquid 
state, so that it is ready to expand again as it enters 
the cylinder. He got an almost complete vacuum 
in the cylinder of his condenser, and a very low 
temperature resulted. 

The arrangement is practically that of Pictet of 
1877. Cailletet in 1883, and Dewar in 1890, and at 
later periods, bear testimony to the good quality of 
Pictet’s early work in the arrangement of apparatus 
they adopted, and which was based on Pictet’s appa- 
ratus, illustrated in this book. 

Cailletet hoped to get oxygen in large quantities by 
the use of this new apparatus, evidently appreciating 
the defect inherent in the Colladon apparatus, which 
quite excluded the idea of operating on large quan- 
tities of gases, and which produced them in a neces- 
sarily non-continuous process. It will be remembered 
that it was the Colladon apparatus which Cailletet 
had adopted in his work of 1877. 

A very ingenious method of producing low tem- 


LIQUEFACTION OF GASES. 201 


peratures was studied by Cailletet, and his paper on 
the subject was published in 1885. He effected the 
evaporation of a liquefied gas with accompanying re- 
duction of temperature by passing a stream of a cold 
gas through it. He placed a tube with ethylene 
within a vessel of dry air, and by blowing cooled 
and dry air or hydrogen through it accelerated its 
evaporation until its temperature fell to —136° C. 
(—212°8° F.) By such a process he produced cold 
sufficient to liquefy oxygen, the latter being com- 
pressed to the requisite extent. 

Working with M. Bonty, in the same year, he 
made quite an elaborate series of experiments on the 
electrical conductivity at low temperatures of a num- 
ber of metals—copper, mercury, silver, aluminum, 
tin, magnesium, iron and platinum. He suggests the 
availability of copper wire as a means for determin- 
ing low temperatures, by its decrease of electrical 
resistance as the temperature falls. This suggestion 
is interesting, in view of subsequent developments. 
A passage from the paper on the subject will be of 
interest : 

“Tt seemed probable that this resistance would 
become extremely small, and consequently the con- 
ductivity very great, at temperatures below —2o00’, 
although our first experiments did not permit us to | 
form a definite idea of that which would occur under 

such conditions.” (Comptes Kendus, vol. c., page 
1189.) 

This isin strict accord with the facts as ascertained 
by other experimenters at later periods. 

In 1888 we have from him a comparison of five me- 
thods of determini: g low temperatures. They were 


202 LIQUID AIR AND THE 


the following: 1. A thermo-couple of iron and cop- 
per. 2. A platinum wire resistance. 3. A thermo- 
couple of pure platinum and of an alloy of platinum 
and rhodium. 4. An ingot of platinum used in con- 
junction with a calorimeter. 5. The hydrogen ther- 
mometer. Boiling water, melting ice and boiling 
methyl chloride, at atmospheric pressure, supplied 
the three fixed points for his scale, and he obtained 
very closely according figures with all of these 
methods. The temperatures of boiling ethylene and 
of boiling nitrous oxide were determined as tests of 
accordance of results. 

Cagniard de la Tour had long ago tried to 
determine the point at which the meniscus of 
water disappeared when it was heated in a 
sealed tube. Pure water attacked the glass tube 
so actively that he could not produce the disappear- 
ance. Cailletet took up the question and tried the 
experiment in a metal tube, with pure water, apply- 
ing a mathematical calculation to determine the 
desired point. The older observer had added 
chemicals to the water to diminish their action on 
the glass. Cailletet discerned in the presence of the 
chemicals a source of error and recognized the im- 
portance of performing the experiment with pure 
water. The description will be found in the Comptes 
Rendus, vol. cxii. 


eae 


LIQUEFACTION OF GASES. 203 


GHAPTER? UX 
SIGMUND VON WROBLEWSKI AND KARL OLSZEWSKI. 


Wroblewski’s life—Banishment from his native country— 
Early scientific work—His association with Olszewski— 
Study of Cailletet’s methods—Their apparatus—Defective 
position of the hydrogen thermometer—Liquefactions of 
oxygen, carbon monoxide and nitrogen—Ethylene data 
—Solidification of carbon bisulphide and alcohol—Deter- 
mination of the critical pressure and temperature of oxy- 
gen—Liquefaction of hydrogen—Use of a thermoelectric 
thermometer—Electric resistance of. metals at low tem- 
peratures—Two liquids from air—Olszewski’s individual 
work—Apparatus for producing liquid oxygen in quan- 
tity—-Comparison of platinum resistance and of hydro- 
gen thermometers—Determination of hydrogen constants. 


As a serious investigator in the realm of the lique- 
faction of gases, no one can be cited who surpassed 
the Polish scientist Sigmund von Wroblewski (pro- 
nounced Vroblevski). He was born in Grodno, 
Poland, in 1845. Grodno is a province which went 
to Russia in the partition of Poland and figures in the 
final partition of 1815 as part of Russia. The king- 


dom of Poland, as arranged by the Congress of 


Vienna at the same time, remained as a separate 
kingdom and intact, although its monarch was the 
Czar of Russia. Then there was a long series of po- 
litical disturbances and bloodshed, culminating in the 
disturbances of 1861-64, and Russia succeeded by 


204 LIQUID AIR AND THE 


the most arbitrary enactments and severe measures 
in suppressing the insurrections and in assimilating 
the so-called kingdom of Poland. 

Wroblewski took part in the uprising as a Polish 
patriot, and was sent to Siberia in 1863, where he 
spent four years. His friends had influence, and 
managed to obtain his release from exile, to the ex- 
tent of being allowed to live in an obscure Russian 
town. Eventually he was released from surveillance 
and went to Germany, visiting Heidelberg and 
Bonn, meeting Kirchoff and Clausius. He had a 
cosmical theory which was not received by either 
the physicists of Heidelberg or of Bonn with any en- 
couragement. At the University of Berlin he con- 
sulted Prof. Helmholtz, who started him to work 
on physical investigation touching his new theory, 
and he completed two years of work under the 
many-sided and brilliant German. He published 
papers bearing on gases which received the honor of | 
attracting the attention of Clerk Maxwell. His prin- 
cipal work on high pressure and low temperature 
applied to gases dates from his knowledge of the 
work of Cailletet on the same subject. He spent 
some time at the Ecole Normale, in Paris, and saw 
and studied Cailletet’s work. He had as associate 
Karl Olszewski (pronounced Olshevski), in the 
writing of the initial of whose Christian name a cer- 
tain amount of confusion obtains, as it is sometimes ~ 
written K, for Karl, and sometimes C, for Charles. 
The association between the two in their early work 
of 1883, and thereabout, is very intimate. In Wrede- 
mann’s Annalen, 1883, is published an article which 
gives the tull account of their first important work 


LIQUEFACTION OF GASES. 205 


in the liquefaction of gases. The authorship is given 
adualform. The title reads in translation, ‘‘ On the 
liquefaction of oxygen, nitrogen, and carbon monox- 
ide, by Sigmund v. Wroblewski and Karl Olszewski.” 
The article, it is impossible to believe, was written 
by anyone but Wroblewski, but when in its course 
anything is to be attributed to a single investigator, 
the expression “‘ezmer von uns” (“one of us”) is 
always used. 

Wroblewski died in 1888. As early as 1684 he 
predicted that liquid air would be the refrigerant of 
the future. His emotions, had he lived to see what 
has been done in the liquefaction of air, can only be 
imagined. The principal reason for his belief in the 
capabilities of liquid air was that it did not have to 
be prepared like carbon dioxide, sulphur dioxide, 
ethyl chloride, or ethylene, that the atmosphere gave 
an inexhaustible supply of matter adapted for the 
function of refrigeration and for use in a cooling 
cycle. 

Wroblewski, in the early days of the liquefaction 
of gases, in 1885, pointed out the method of the 
future. In the light of what has been since then 
accomplished, a translation of his remarks from 
the Wiener Sitzungsberichte reads almost like a pro- 
phecy: 

“The essential step forward which should be 
made with regard to the extension of the method is 
to change it so that we may be prepared to pour 
oxygen as we pour ethylene to-day. It is my convic- 
tion that the thing will only be successfully carried 
out when we return to Pictet’s method, and by 
cycles of various liquefied gases make a cascade of 


206 LIQUID AIR AND THE 


temperatures whose last step will produce the stream 
of liquefied oxygen.” 

It is precisely by carrying out such a line of work | 
that Dewar won fame for himself and the Royal In- 
stitution. 

The carefully prepared article in Wiedemann’s An- 
nalen is an example in its way of how a scientific 
paper should be written. There is in its aspect and 
tenor such sincerity and so careful an avoidance of 
anything like self-assertion that it is at once convinc- 
ing and impressive. 

These investigators were subsequently attached to 
the University of Cracow, and much of their work 
dates from that city. The results are published in 
various languages. There is no need to study Polish 
to read them. 

“One of us,” Wroblewski, while in Paris studied 
Cailletet’s apparatus and methods, and had an ap- 
paratus made by a Paris mechanic, E. Ducretet, for 
the prosecution of researches on liquefied gases. The 
point is made that it is superior to the Cailletet ap- 
paratus of that early date because it could be used 
with five or six times as much gas as could be used 
in Cailletet’s apparatus. 

The apparatus may be considered in two divisions 
—one the condensing apparatus by which the gas to 
be experimented on was subjected to pressure, the 
other the refrigerating apparatus for cooling it be- 
low the critical temperature. 

We reproduce the cuts of the apparatus from 
Wredemann’s Annalen. It will be seen that the gas 
compression apparatus is practically a copy of Cail- 
letet’s apparatus, so that the apparatus goes back to 


207 


LIQUEFACTION OF GASES. 


aah 
' —— 


—= 


a 


I 
Wily —— se 


f 
MMMM 


a / 


In the gas refrigerating por- 
LZ 


tion will be found a reminder of Pictet’s circuits, not 
J 


Z Wh 
Wroblewski and Olszewski’s Gas 
Compression Vessel 


me) 
a 
= 0. SOLO. ge ah Agee Fs a, ro Ee aS, et eh iy ans ce ee ana ee 
Bra Deco Oe ae re HS a AR eco ere Tore coe ae 
mony 9 St eS Se AO eo gee Pies S$ Bde z 
Fatale nA BESE Oo 2a Oo eee ace cei a 
Rms ec eoP rt 'vagh ve oe SRCU Sak ator ae Me Sop ae OO Sl at ees 
oO DSN . ct O — o mH 8 Dm & a MW 4. 
st gy GG " or Summa rPoe Pad or ceeg Sern en eae og 
© tO. + Aa QD Poin, = - on a, ) fs} 
ra n 2 HE A oa Bo, Cp OW 8 Bea ope 0 Ve ae So oa 
par Go Ay FS neh PO aS SO Gok fee 2 B88 Oo bon ee | fotos Ste 


208 LIQUID AIR AND THE 


centimeters (23°2 inches) deep and 85 centimeters 
(3°4 inches) wide. ¢ ando isa bronze piece which 
forms a tight connection between the gas tube, z, 
and the upper tube, ¢, 7, g,¢ A very strong steel 
tube runs through the orifice in the piece, d. To 
get it in place the horizontal portion of the piece in 
question was sawed through horizontally in the line, 
e,e,and bored downward from g and f. The steel 
tube was inserted in place, a groove along the line, 
e, é, receiving it. The piece which was sawed off 
was replaced and brazed in its former place, so as 
to surround the steel tube. . 

At the end, #, the steel tube expands, and they 
glass gas tube, z, is cemented into it. At & the 
bronze steel-lined piece has aconicalend. mis a 
glass tube cemented in place, and all is secured by a 
coned piece, /, with screws, 7, as shown, the Screws 
uniting all parts to an airtight joint. 

At-patube is connected which leads to a force 
Put: 

The next illustration shows how the apparatus was 
set up for the liquefying of gases in the downwardly 
extending tube from the compressing apparatus. 
This cut is also an exact reproduction of the cut 
given in Wiedemann’s Annalen. 

We have, as before, the vessel, z, with its steel con- 
taining vessel, 6, only the top of which is shown. 
The capillary tube, g, was o’g centimeter (0°36 inch) 
external diameter and a little over o'2 centimeter 
(o'08 inch) internal diameter. The glass vessel, z, 
was filled with the gas to be experimented with. 

A jar, y, has calcium chloride at its bottom to keep 
the air within it perfectly dry. A second vessel, s, 


LIQUEFACTION OF GASES. 209 


is set into it airtight with an india rubber stopper. 
The vessel, s, is provided with an india rubber stop- 
per of its own, perforated for three tubes. One is 


AIT ORD 


NN RLS 
= 


a} 


. 
NZ 
LL 


Uv 


g 
Z 
ZN 
Z 
g 
Zs 


Wroblewski and Olszewski’s Apparatus for 
Liquefying Gases. 


the end, g, of the gas tube, 2, the other the stem of the 
hydrogen thermometer, ¢. The third receivesa T 
shaped tube, «. Liquid ethylene is contained in the 


210 LIQUID :ATRVAND. THE 


cylinder, x, where it is kept cool with ice and salt. 
The liquid ethylene is withdrawn at a, through a 
thin tube, w. This tube is coiled into a cooler, 0’, 
charged with liquid and solid carbon dioxide. This 
brings it down to a very low temperature. 

As needed it is drawn into the vessel, s. An air 
pump connected to the T tube, w, by the tube, z, 
produces an almost full vacuum in the vessel, s. The 
upper end of the T tube is provided with an india 
rubber cork through which the tube, w, passes air- 
tight, the liquid ethylene dropping from c. 

The gas to be experimented on was introduced into 
the tube, z, mercury was contained in the vessel, 4, 
and the pressure was increased to any desired extent 
by pumping water into 4. The end of the gas tube, 
which was sealed and bent down, was cooled by ad- 
mission of the cooled ethylene into the vessel, s, and 
this vessel was pumped out by an air pump, so that it 
was kept down to a pressure of but 24 millimeters of 
mercury, which is a small fraction of an atmosphere. 
The ethylene, when first admitted to the vessel, s, 
boiled tumultuously, but soon quieted down and 
kept slowly boiling, thereby producing a a low 
temperature. 

Each experiment required 200 to 300 grammes of 
ethylene and about 400 grammes of solid carbon 
dioxide. Very little ethylene was lost. 

The apparatus worked well. The only trouble 
chronicled was due tothe mercury freezing in the 
capillary tube, which brought about an explosion 
which did no great injury. 

The temperatures were taken by the hydrogen 
thermometer, ¢, whose bulb, it will be observed, is 


LIQUEFACTION OF GASES. 211 


placed in the refrigerating vessel, not in the gas ex- 
perimented with. Thus the temperature recorded 
is that of the environment of the sample, not that of 
the sample itself, which is a defect worthy of com. 
ment. 

While on the subject of thermometers, it may be 
noted that there occurs in the Wiedemann’s Annalen 
article an interesting statement to the effect that 
Natterer told “one of us,” orally, that he filled his 
low temperature thermometer with phosphorus 
chloride. This gives us a glance at the work of a 
preceding generation and is mentioned elsewhere 
in this book. 

The results obtained with this apparatus were very 
good. Oxygen liquefied at —130° C. (— 02° F.) 
and at a pressure of a little over 20 atmospheres. It 
was a colorless fluid, the slight blue tint not showing, 
presumably because of its slight amount. It had a 
flatter meniscus than that of carbon dioxide. On 
reducing the pressure to a relatively small degree 
it foamed, evaporated from the surface, and on 
further reduction, boiled throughout its entire mass. 

The work of these investigators at about this 
period is the subject of other papers in the Comptes 
Rendus and elsewhere. 

In the Comptes Rendus, vol. xcvi., is given the dis- 
patch announcing Wroblewski’s liquefaction of oxy- 
gen. It was received by M. Debray, secretary of the 
Academy of Sciences, on April 9, 1883, from Cracow. 
It reads as follows: 

“ Oxygéne liquéfié, completement liquide, incolore 
comme l’acide carbonique. Vous recevrez une note 
dans quelques jours.” 


212 LIQUID AIR AND THE 


“Oxygen liquefied, completely liquid, colorless 
like carbonic acid. You will receive a note in a few 
days.” 

The “note” which follows is given in the same 
volume of the Comptes Rendus and alludes to Cail- 
letet’s ethylene paper (ibid., vol. xciv., page 1224). 
The authors say that Cailletet did not fully satisfy 
himself. Wroblewski and Olszewski, with apparatus 
made by “one of us”’ (‘uz de nous’), who was in this 
case Wroblewski, and using a quantity of oxygen, 
effected the liquefaction. They found liquid oxygen 
colorless and transparent, very mobile, and giving a 
sharp meniscus. 

With boiling ethylene in approximate vacuum 
they got a temperature of —136° C. (—212°8° F.) by 
the hydrogen thermometer. They found that at the 
atmospheric pressure ethylene boils at —102° to 
—103° C. (—151°6° to 153°4° F.), and not at —105° C. 
(—157° F.) The following data for oxygen were 
determined on April 9g: 

At temperature of —131°6° C. (—204’9° F.) begins 
to liquefy at 25°5 atmospheres. 

At temperature of —133'4° C. (—208'1° F.) begins 
to liquefy at 24°8 atmospheres. 

At temperature of —135°8° C. (—212'4° F.) begins 
to liquefy at 22°5 atmospheres. 

They took advantage of their ethylene apparatus 
to try some other experiments in the direction of 
freezing carbon bisulphide and alcohol. 

Carbon bisulphide froze at about —116° C. 
(—176'8° F.), alcohol became thick like sirup at 
about —129° C. (—200°2° F.), and froze a degree 
lower, —130° C. (--202° F.) . 


LIQUEFACTION OF GASES. 213 


On April 16, 1883, another dispatch was received 
by the secretary of the Academy of Sciences, telling 
of the same investigators’ liquefaction of nitrogen: 

“Azote refroidi, liquéfiée par detente. Menisque 
visible, liquide incolore.” | 

“Nitrogen cooled, liquefied by release. Visible 
meniscus, colorless liquid.” 

The note which gives the details of the liquefac- 
tion of nitrogen says that they exposed nitrogen at 
—136° C. (—212°8° F.) to a pressure of 150 atmo- 
spheres. On sudden release there was a tumultuous 
ebullition (“ aufbrausen”’) like that of carbon dioxide 
in a Natterer’s glass tube of carbon dioxide (page 23) 
when it is plunged into water which is a little 
warmer than the critical temperature of carbon 
dioxide. Then they tried a partial release from 
pressure, lowering it to 50 atmospheres, when the 
nitrogen liquefied completely with a meniscus. It 
remained a few seconds only. It was colorless and 
transparent. 

On April 21, 1883, the following dispatch was 
received by the Academy from the same investi: 
macors: 

“Oxyde de carbone liquéfié dans les mémes con- 
ditions que l’azote. Ménisque visible. Liquide in- 
colore.” 

“Carbon monoxide liquefied under the same con- 
ditions as nitrogen. Meniscus visible. Colorless 
liquid.” 

Hydrogen they failed to liquefy. It was cooled 
to —136° C. (—212'8 °F.), compressed to 150 atmo- 
spheres, then was suddenly released, but not evena 
mist appeared. Boiling oxygen is recommended as 


214 LIQUID AIR AND THE 


a cooling agent, but the impetuousness with which it 
boiled was a great obstacle to its use. Even at one 
atmosphere of pressure it proved uncontrollable. 
The duration of its ebullition was very short, and 
this proved an objection. Eight years later, in 1891, 
Olszewski overcame this trouble by bubbling hydro- 
gen through it gradually. Cailletet’s production of 
cold by bubbling a gas through a volatile liquid, as 
described on page 201, may be noted also. By a 
thermo-electric couple its temperature was deter- 
mined. It is given as —186° C. (—302°8° F.) 

Nitrogen was compressed and cooled with boiling 
oxygen without result, but on sudden release from 
pressure it formed snow-like crystals of remarkable 
S1ze. | 

In 1883 Wroblewski and Olszewski attacked the 
problem of determining the specific gravity of pure 
oxygen. They introduced a known quantity of 
oxygen into their apparatus and liquefied it as com- 
pletely as possible. This gave them an approxima- 
tion, if they neglected to take into account the un- 
liquefied gas which lay above the liquid. To deter- 
mine what value this unliquefied portion had, a con- 
trol experiment was done with liquid carbon diox- 
ide whose specific gravity was known, the experi- 
menters using Andréeff’s determination (Lzebzg’s An- 
nalen, vol. cx., page 1). The calculations are too com- 
plicated. to -be here reproduced: » The -resultvobs 
tained for oxygen at about —130° C. (—202° F.) and 
the pressure of liquefaction was C899. 

Wroblewski, still longing to produce liquid oxy- 
gen in quantity, says, in December, 1883, that it is 
merely a question of appliances to produce liquid 


LIQUEFACTION OF GASES. 215 


oxygen, but acknowledges that he has never suc- 
ceeded in producing oxygen in the condition of a 
static liquid. Any attempt to use the refrigerating 
effect of oxygen, he said, involves its use at the in- 
stant of production or cessation of pressure. Such 
danger of explosion attended attempts in this direc- 
tion that masks were worn. 

_ A valuable suggestion would seem to be the one 
made in 1884, when Wroblewski suggests the use of 
liquid marsh gas as a refrigerant. In its properties 
it is adapted to fill the gap which exists between 
liquid ethylene and liquid oxygen. The honor of 
being the first in the field with this suggestion 
was afterward claimed by Cailletet. Dewar, how- 
ever, was able to show that he had suggested the use 
of liquid marsh gas as far back as 1883, which ante- 
dates Wroblewski, and Cailletet’s date goes back 
to 1881. 

After this period the two scientists appear as in- 
dividual workers. The path started on the lines of 
Cailletet’s and Pictet’s work led to direct experimen- 
tal determinations, but these appear in later work. 
The early apparatus, just described, did not lend itself 
to thoroughly reliable temperature observations. I[n- 
direct methods of dealing with problems had to be 
used, and in some cases data were reached on almost 
purely theoretical grounds. This was done to some 
extent quite recently, and the hydrogen data were 
determined with fair approximation partly from a 
theoretical basis. 

Much ingenuity appears in the methods of attack- 
ing the problems which presented themselves in 
the course of their experimentation. Asan example 


216 LIQUID AIR AND THE 


may be cited the determination of the critical tem- 
perature and pressure of oxygen (Comptes Rendus, 
vol. xcvii.) 

Oxygen gas was liquefied in the downwardly bent 
tube, g, of the apparatus, page 209, by the aid of 
boiling ethylene contained in the vessel, s, as already 
described. As the oxygen liquefied its level rose in 
the tube, g, and eventually reached a point above 
the level of the liquid ethylene in s. Now it is evi- 


= 


dent that, as the liquid oxygen reachesa pointin the | 


gas tube above the ethylene, the temperature of its 
upper layers is higher, and the more it rises, the 
higher is this temperature. As the temperature in- 
creases, the pressure necessarily rises. 

At last a point is reached when evidences of the 
critical state begin to show themselves. The menis- 
cus flattens, the line of demarkation between liquid 
and gas becomes indistinct and at last entirely dis- 
appears. The only way to trace the position of any 
separating level is by the difference of refractive 
power of the different layers in the tube. The de- 
scription as given by Wroblewski exactly describes 
the phenomena observed in a Natterer’s tube (page 
23); | 

If the pressure is lowered, the temperature of 
the oxygen falls, liquefaction ensues, and the men- 
iscus again forms. Working in conjunction with 
Olszewski, the investigator found that this phenome- 
non of the critical state occurred always at about 
the pressure of 50 atmospheres. 

The pressure of oxygen under these conditions is 
so high and its temperature so low that it appeared 
desirable to exercise some sort of a check upon this 


LIQUEFACTION OF GASES. 217 


experiment. Thesame tube was charged with liquid 
carbon dioxide overlaid by the gas, in exact ana- 
logue with the conditions of the oxygen experiment. 
The boiling ethylene was replaced by melting ice, and 
warm water at 50° C. (122° F.) surrounded the upper 
part of the tube. Hence, within the length of the gas 
tube the temperature had a range of 50° C. 

Pressure was applied, and at 35 atmospheres traces 
of liquid carbon dioxide appeared in the bottom of 
the tube, which was the cold part. The gas kept on 
liquefying until the liquid rose above the level of the 
melting ice and began to reach the warm portion of 
the gas tube. The pressure increased as the lique- 
- fied carbon dioxide attained in its upper layers a 
higher temperature. 

As the pressure approached 76 atmospheres the 
meniscus became flat, then indistinct, and eventually 
disappeared. The critical state was reached. On 
-lowering the pressure, the liquid diminished in 
amount, the level fell, and the upper layer reached a 
cooler part of the tube. The meniscus at once showed 
itself again. The appearance and disappearance of 
the meniscus evidently took place at a point of the 
tube where the critical temperature existed. The 
pressure in the apparatus when the phenomena 
described took place was the critical pressure. 

The attempt was made now to ascertain the criti- 
caltemperature of oxygen—a far more difficult factor 
to determine. A small quantity of oxygen was lique- 
fied in the apparatus, so that it was below the level of 
the liquid ethylene. The latter was boiling under 
exhaustion so as to give a very low degree of 
temperature. The exhaustion was stopped and the 


218 LIQUID AIR AND THE 


temperature of the ethylene began to rise. The 
meniscus was watched. 

Two things were occurring in the tube. The tem- 
perature was rising and the pressure increasing as 
the ethylene became warmer. Sooner or later the 
balancing point, the critical state, would be reached 
and the disappearance of the meniscus gave the indi- 
cation. This was watched for, the temperature of 
the ethylene being constantly observed. 

The observations were extremely difficult, and 
Wroblewski gives the figure of —113° C. (—171°4° 
F.) in his own words, “as the first approximation to 
the critical temperature of oxygen.” The tempera- 
ture we now know was too high by nearly 6° C. 

Cailletet had brought before the French Academy 
of Sciences his liquefaction of hydrogen (page 184). 
He had on release from pressure obtained a mist or 
fog, which he claimed was due to liquid poses 
Naturally some doubt was felt about it. 

Wroblewski had tried it, and in an early number 
of the Comptes Rendus—early as regards its date— 
referring to the history of the liquefaction of oxygen 
and of the “permanent gases,” says that he tried 
Cailletet’s experiment and failed. 

On January 4, 1884, the following dispatch from 
Wroblewski was received by the French Academy 
of Sciences: 

“ Hydrogéne refroidi par oxygéne bouillant s’est 
liquefié par detente.” 

“Hydrogen cooled by boiling oxygen has been 
liquefied by release.” 

Debray commented on the dispatch and says that 
this experiment confirms Cailletet’s experiment. 


LIQUEFACTION OF GASES. - 219 


In the Comptes Rendus of February, 1884, Wro- 
blewski tells of his liquefaction of hydrogen. He 
compressed hydrogen to 100 atmospheres in a 
glass tube whose general dimensions were from o*2 
cm. to 0°4 cm. (0°08 inch to o*16 inch) in internal 
diameter and 2 cm. (0°8 inch) external diameter. It 
was arranged for very sudden release of pressure. 
The tube was surrounded with boiling oxygen in 
order to reduce the temperature of the hydrogen. 
On sudden release of pressure the hydrogen gave 
the mist as in Cailletet’s experiment of 1882. 

To determine the temperature a thermocouple was 
used, which was connected to a galvanometer which 
could show a potential difference of gypsay_ Volt, 
which corresponded to half a degree on the ther- 
mometric scale. It was standardized by comparison 
with a hydrogen thermometer. 

It was known that the electric resistance of metals 
falls with the reduction of temperature. As early as 
1885 Wroblewski had tried silk-covered copper 
wire, cooled to a temperature of —200° C. (—328° 
F.), and found that its resistance was less than one- 
hundredth of what it was at the temperature of 
boiling water. He says that oxygen and nitrogen, 
in the liquid state, are among the most perfect insu- 
lators known. He says that the electric resistance 
of copper, at a temperature approaching that of boil- 
ing nitrogen, tends to become zero—the conduc- 
tivity approaches perfection. 

This view has been very prominently brought for- 
ward again by Dewar and others, and Elihu Thom- 
son goes so far as to believe that in liquid gases a 
useful reducer of electric resistance for power div- 


220 ; LIQUID AIR AND THE 


tribution may be found. It is certainly very capti- 
vating to think of a thin copper wire in a pipe filled 
with liquid air carrying the energy of Niagara Falls 
over hundreds of miles of country. 

An experiment which excited much comment, and 
which now, in these days of wholesale liquefaction 
of air, is almost lost sight of, was described by Wro- 
blewski, who, in 1885, in liquefying air, produced 
from it two liquids superimposed and which re- 
mained separate for some minutes. He managed to 
withdraw, by a metallic tube, samples from each layer 
for analysis—rather a delicate operation, it would 
seem. On analysis, the lower layer, after gasifica- 
tion, gave a little over one-fifth of its volume of oxy- 
gen (21°28 per cent. to 2I°5 per cent. oxygen). The 
upper liquid gave a little over seventeen-hundredths 
of its volume of oxygen after gasification (17°3 per 
cent. of nitrogen). 

Wroblewski had used various thermometers for 
determining the low temperatures which he obtained 
in his experiments, the hydrogen-filled thermometer 
seeming eventually to give him most satisfaction. 
Cailletet had used various thermometers, finally tend- 
ing to the hydrogen one. Pictet had adopted a very 
indirect method of calculating temperatures, and the 
thermo-couple had also been employed, as we have 
just seen. 

In 1885 Wroblewski published a paper embodying 
his experiments on the relations existing between 
temperatures as determined by the hydrogen ther- 
mometer and a thermo-electric couple of copper and 
German silver. 

After this year but little appears under the name of 


LIQUEFACTION OF GASES. 1 UZ2y 


this distinguished investigator. He seemed to pos- 
sess the rare faculty of not disputing with any of his 
confréres. The disputes as to priority in the lique- 
faction of gases are very numerous and extend over 
the greater part of a century. Wroblewski was for- 
tunate in not being involved in any of them, as far as 
his own statements are concerned at least. 

Wroblewski and Olszewski worked together for a 
number of years, but the latter scientist continued 
the same line of work alone up to a recent period. 
In the Philosophical Magazine, March, 1895, he pub- 
lished a résumé of his work, incidentally giving vent 
to a certain amount of feeling and attacking Dewar 
and Pictet. 

In 1885 Olszewski made what may be called an 
approximate liquefaction of hydrogen. He mixed 
two volumes of hydrogen with one volume of oxy- 
gen and liquefied the mixture successfully. The 
mixture was colorless. On release from pressure it 
lost most of its hydrogen. The residual liquid lasted 
for some time at the atmospheric pressure. 

He is much interested in showing that he pro- 
duced oxygen in quantity large enough to pour from 
one vessel into another. In October, 1890, he 
produced 100 cubic centimeters before an au- 
dience, and in July of the succeeding year, also 
before an audience, he produced 200 cubic centi- 
meters. He lays great stress on this achieve- 
ment. 

His apparatus, by which he produced oxygen in 
what were large quantities for the period, was very 
simple. Its essential feature was the use of a steel 
cylinder of small capacity in which the oxygen was 


222 LIQUID AIR AND THE 


liquefied. This took the place of the glass tube in 
which the gases were liquefied in the original Wro- 
blewski and Olszewski experiments. 

In 1883 and the subsequent years the two asso- 
ciated investigators had liquefied gases in glass 
tubes. The almost capillary tube of their early ex- 
periments was changed sometimes for a larger one. 
Thus the following are given as the dimensions of a 
tube in which many liquefactions were carried out: 
The tube was 30 centimeters (about 12 inches) long 
and 14 to 18 millimeters (0°56 to 0°72 inch) in in- 
ternal diameter. The walls were 3 to 4 millimeters 
(o'12 to 0°16 inch) thick. 

All the “permanent” gases then known, from 
which argon, helium and the companions of argon 
must be excluded, for they were not yet discovered, 
had been liquefied in this apparatus, as already 
described, and nitrogen, carbonic oxide, nitric oxide 
and marsh gas had been solidified. 

It will be observed, especially if the cut of the 1883 
apparatus (page 209) be inspected, that no means 
were provided for drawing off the small amount of 
_ liquefied gas which might be produced in the glass 
tube. If an attempt had been made to substitute a 
large glass bulb for the tube, it would never have 
stood the strains due to changes of temperature and 
high pressure. By the repetition of numberless 
liquefactions, the conditions necessary to produce 
them became so accurately known that it was no 
longer necessary to see the liquefaction to know 
that it was produced. The necessity for a trans- 
- parent vessel had ceased. 

Olszewski accordingly substituted for the sla 


LIQUEFACTION OF GASES. 223 


tube a small steel reservoir. This would stand the 
pressure without danger of explosion, and was so 
good a conductor of heat that the most sudden 
changes of temperature had not the least effect upon 
it in the direction of causing it to break. 

This apparatus was described in 1890 in the Budle- 
tin internationale de 1 Academie de Cracovie. While 
Olszewski, in the Philosophical Magazine article, seems 
to indicate that his work has not been fully enough 
appreciated, he makes very evident one reason. He 
gives the list of his original papers. So many of 
them appeared in the Cracow Bulletin, whose title is 
given above, that they were deprived of the circu- 
lation which was their due and which would have 
been secured by a wider publication in the German, 
French and English scientific annals. 

But Olszewski’s steel reservoir, like Pictet’s lque- 
faction tube, was provided with a cock by which its 
contents could be withdrawn, and this certainly was 
an advance over a sealed glass tube. The proba- 
bilities are that in 1883 the possibility of handling 
liquid gases at atmospheric pressure like so much 
water was undreamed of. 

The mechanically bad feature of Pictet’s old ap- 
paratus was present in this one, which comes some 
thirteen years later. The liquid was drawn from a 
reservoir in which it was confined under enormous 
pressure. The outrush of the almost uncontrollable 
fluid must have given some trouble to the experi- 
menter. ) 

We give the diagram of the steel reservoir appa- 
ratus with which oxygen was liquefied in quantities 
sufficient to pour from one vessel into another. 


224 LIQUID AIR AND THE 


A isacylinder of oxygen gas compressed to 100 
atmospheres. It is connected by a tube to the steel 
reservoir, 8. From the lower end of the steel reser- 
voir a tube with stopcock, 4, descends. A gauge,.a, 
indicates the pressure of the oxygen. It is obvious 
that any considerable diminution of pressure would 
indicate liquefaction. 


ag : 


Ge pees 


Olszewski’s Liquefaction Apparatus of 1890. 


The reservoir, 4, is contained in a double-walled 
vessel, C, hermetically closed at the top. From it 
one tube, g, runs to an exhausting pump. This tube 
has a cock, g, and vacuum gauge, v. Another tube, 
¢, runs to an ethylene cylinder, D. This tube has a 
stopcock, ¢, and is bent into a coil between C and D. 


LIQUEFACTION OF GASES. 225 


The coil is contained in a vessel, £, which is charged 
with a mixture of ether and solid carbon dioxide. 
A tube, a, leads from this vessel, which is absolutely 
tight, to an exhausting pump. JZ contains liquid 
ethylene, which is kept cold by ice and salt mixture 
in the outer vessel, /. 

The oxygen under high pressure filled the steel 
vessel, B, which was quite small, of but a few ounces 
capacity. Here it was subjected to the refrigeration 
due to the liquid ethylene, cooled by exhausted carbon 
dioxide and ether, and also subjected to exhaustion, 
so as to have its temperature. greatly reduced by 
boiling. The intense cold, which was below the 
critical temperature of oxygen, rapidly liquefied it 
under pressure, and soon the vessel, 4, filled with 
the liquid. It could then be drawn off by opening 
the cock, 8. 

By opening and shutting the cocks the apparatus 
could be manipulated very readily, and the pressure 
gauge, a, and vacuum gauge, v, gave certain indica- 
tions of the progress of operations. If the apparatus 
is analyzed and reduced to its elements, it will be seen 
to be a simplification of Pictet’s apparatus of 1877, 
simplified by the suppression of pump circuits and 
by the use of compressed gases. It will be seen to 
be much the same as Dewar’s apparatus of 1883 
(page 236), and the latter expresses himself as of the 
opinion that the substitution of the steel reservoir for 
the glass. tube which he employed was not a very 
important change. 

To keep this delivery under some control, the out- 
let tube from the steel oxygen vessel had lateral 
openings. This prevented the stream of liquid from 


226 LIQUID AIR AND THE 


rushing out against the bottom of the vessel and 
driving out the contents as fast as received. 

It is impossible within the limits of this work to © 
give the entire work of any investigator. Olszewski 
determined many constants, by many methods, and 
the general abstract of his work, with table of con- 
stants determined and bibliography or list of his pa- 
pers, may be found in the Philosophical Magazine for 
1895. 

For determining low temperatures he used as a 
‘matter of preference the hydrogen thermometer, and 
used it to standardize a platinum resistance thermo- 
meter when the temperature fell too low for the 
hydrogen instrument. But he distrusts all except 
the hydrogen thermometer, except under limited and 
defined conditions. Extrapolation he naturally sus- 
pects, and, on account of variations in specific heat 
as lower temperatures are reached, he has little con- 
fidence in calorimeter methods. 

During his investigations he was troubled with 
bursting tubes. His work, like that of other investi- 
gators, was not of the safest order. 

James Clerk Maxwell, one of the most illustrious 
physicists and mathematicians of England, had 
doubted the possibility of liquefying hydrogen. 
Faraday had not felt so. He believed that it might 
yet be accomplished, and expresses himself in rather 
uncertain phrase concerning it. Olszewski had no 
hopes of liquefying it in volume or as “ static hydro- 
gen.” The lesson of Cailletet’s production of cold 
by release from pressure seems to have been lost to 
the world, only to be’successfully applied within the 
last five years by Tripler, Linde, Hampson and 


LIQUEFACTION OF GASES. 227 


Dewar. But without attempting to liquefy it in 
large volume, Olszewski tried to determine the con- 
stants of liquid hydrogen. Now, his temperatures 
ran so low that he was forced to use a platinum 
resistance thermometer, which he compared with a 
hydrogen thermometer, with the following result : 


Electrical resistance of 


Temperature by hydrogen platinum resistance 
thermometer. thermometer. 
oy AOC e Sl eS Weer es Ce haere 1000 ohms. 
Se (LOS Boe Es) ait pcs ermie 9.5 Sone 
Bem 2 eek e200 Gas) iene wats oie m os nix Pees 
= aa TRE | ORTA ESE i te Sealed ea ern aera ee AGS ate 


This shows the decrease in electrical resistance due 
to reduction of temperature which is utilized as a 
thermometric factor. But moreis shown. The fall 
in electrical resistance per degree fall in tempera- 
ture grows greater as the temperature descends. 


Thus: 
Ohms. 


Between 0° and —78:2°C. the fall per degree is 2°557 
66 —78°2° 66 —182'5° C 66 66 66 66 2°655 
(6 —182'5° 66 —208'5° @ (6 6 66 66 2°692 


The last figure was adopted for the extrapolation, 
or carrying out the scale beyond the limits of the 
experiment. 

He found for hydrogen a critical temperature of 
—234'5° C. (—390'1° F.) and a boiling point at atmo- 
spheric pressure of —243°5° C. (—406°3° F.) The 
lowest static temperature Olszewski claims to have 
attained is —225° C. (—373° F.) The hydrogen tem- 
peratures were of exceedingly brief duration. 

The method adopted for reaching this figure de- 


228 LIQUID AIR AND THE 


pended on the observation that if a gas is exposed to 
high pressure and is then cooled to a temperature 
not far from the critical temperature, a slow reduc- 
tion of pressure will bring about liquefaction of the 
gas. The appearance of a mist indicated the lique- 
faction. The result of numerous experiments with 
hydrogen showed that this mist appeared always 
at exactly the same pressure if the experimenter 
started with a high enough pressure. 

Thus he varied the initial pressure all the way 
from 80 to 140 atmospheres by Io atmospheres at a 
time, cooled the compressed gas to —-211° C. 
(—347°8° F.) and suffered the gas to expand, watching 
the change in pressure as it did so, and watching for 
the mist. This mist always showed itself at 20 atmo- 
spheres of pressure, whether the initial pressure was 
high or low, provided it did not range below 80 at- 
mospheres. 

If the initial pressure did fall below this point then | 
the pressure at which liquefaction took place also fell, 
and, starting from initial pressure of 50, 60 and 7o 
atmospheres, the mist appeared at pressures of 14, 16 
and 18 atmospheres respectively. Allconstancy was 
lost. 

Therefore, Olszewski accepted 20 atmospheres as 
the critical pressure of hydrogen, and thence de- 
duced the conclusion that hydrogen liquefying at 
20 atmospheres had the critical temperature. As 
he could always produce the slight evidences of 
liquefaction at this pressure in the small glass tube, 
he believed that he could always produce liquid hy- 
drogen at the critical temperature by establishing 
the conditions described. 


LIQUEFACTION: OF GASES. 229 


The only trouble was that such a minute quantity 
of hydrogen was liquefied in his glass tube that it 
was impossible to determine its temperature. He, 
therefore, resorted to his steel vessel apparatus (page 
224), established the proper conditions of initial pres- 
sure and temperature, slowly reduced the pressure 
to 20 atmospheres, and took the temperature of the 
hydrogen in the steel vessel. 

He saw no liquefaction, for the steel vessel hid its 
contents. He established the conditions which had 
always produced the mist in the transparent glass 
tube, and he relied upon the large size of the steel 
vessel to give enough liquid hydrogen to affect the 
electric resistance thermometer which he employed. 

Dewar, after producing liquid hydrogen in. quan- 
tity so that it could be poured from vessel to vessel, 
and so that its temperature could be accurately de- 
termined, comments unfavorably on Olszewski do- 
ing his work-in an opaque vessel. Although, too, 
Olszewski’s assumptions seem rather forced, and led 
him to too high a critical pressure figure, his results 
are surprisingly good, and compare well with Wro- 
blewski’s calculated ones and Dewar’s presumably 
more accurate ones. 


ee 


LIQUEFACTION OF GASES. 231 


PCHAPTER: XI 


JAMES DEWAR. 


Dewar’s life and education—His associates—Controversies 
with Cailletet as to priority—Early liquefaction appa- 
ratus—Solid nitrous oxide as a refrigerant—Royal Inst1- 
tution apparatus—Cooling cycles employed—Laboratory 
apparatus—Vacuum vessels—Air as a heat conveyer— 
Experiments with incandescent lamps—-Reflection of ether 
waves from vacuum vessel-_Keeping power of vacuum 
vessels—The Dewar vacuum—lIts extraordinary perfec- 
tion—Analogy with population of earth—Experiment in 
slow diffusion of mercury vapor—Incidental production 
of vacuum vessels—Elasticity and strength of metals at 
low temperatures—A pparatus used—Elongation of metals 
when stressed at low temperatures—Determination of 
specific and latent heats of liquefied gases—Gas jet ex- 
periments—Low temperatures thus obtained—Freezing 
air—Large jet apparatus—Analysis by liquefaction— 
Liquefaction of fluorine—Ljiquefaction of hydrogen and 
helium—Experiments to show the intense cold. 


James Dewar was born in 1842, in Kincardine-on- 
Forth. He was educated at the Dollar Academy, 
and subsequently at the University of Edinburgh. 
He acted as assistant in chemistry to Sir Lyon 
Playfair in the University of Edinburgh, where the 
former was Professor of Chemistry. He also stu- 
died in Ghent under Auguste Kekulie. He has had 
many honors accorded him. For sixteen years he 
has been Jacksonian Professor in the University of 


232 EIQUTD*ArR TANT San 


Cambridge. He is Fullerian Professor of Chemistry 
in the Royal Institution of England, thus being 
Iaraday’s successor. 

The list of papers by Prof. Dewar and his col- 
leagues relating to investigations at low tempera- 
tures is a long one, extending from 1874 down to the 
present time, and including nearly eighty titles. 
His colleagues in this work comprise Professors G. 
D.. Liveing, J. A. Fleming and Moissan, Most of 
the papers are by Dewar alone. 

Dewar had been interested in calorimetry for a 
long time, and had used a vacuum vessel as an insu- 
lator in calorimetrical experiments in 1874, at the 
University of Edinburgh. This date was brought 
out in a claim of Cailletet, who thought that he 
antedated Dewar in this device. Had it not been 
for the old Edinburgh experiments, the French 
scientist would probably have carried his point. 

_ An early reference of Dewar’s involved him in a 
second controversy with Cailletet. At the 1833 
meeting of the British Association for the Advance- 
ment of Science he had pointed out the advantages 
of a liquid of low critical pressure, such as liquefied 
marsh gas, for the production of intense cold. The 
critical temperature of this gas he put at less than 
—100° C. (—148° F.), with a corresponding pressure 
of only 39 atmospheres. He then stated that he 
hoped soon to approach the absolute zero by the use 
of this refrigerant. 

Dewar set considerable store by this utterance, as 
he had hoped to prove by it his priority in the use 
of liquid marsh gas for the production of cold, which 
priority was claimed by Cailletet. 


LIQUEFACTION OF GASES. 233 


In 1885 he and Cailletet had a discussion or inter- 
change of communications on the subject of the 
priority in the use of liquefied marsh gas, Dewar re- 
ferring to his British Association remarks as pub- 
lished in Mature in 1883, and Cailletet referring 
to a sealed communication deposited by him with 
the French Academy of Sciences, dated 1881. 

As a portion of his duties at the Royal Institution, 
Dewar had to lecture on chemistry and physics, and 
naturally felt called upon to show liquid oxygen to 
his audiences. The work of Cailletet, Pictet, Wro- 
blewski and Olszewski was still fresh and in pro- 
gress. Accordingly, Dewar -had arranged a lique- 
faction apparatus on the lines followed by the last 
named investigators for exhibiting liquid oxygen to 
his audiences. These lines, it will be remembered, 
involved originally a combination of Cailletet’s and 
Pictet’s apparatus. As their work progressed, Cail- 
letet’s apparatus became less a feature of it, but 
Pictet’s system of successful cooling cycles was 
preserved. 

This feature is prominent in Dewar’'s early appa- 
ratus, and has always becn retained up to the present 
time. Pictet set the example, which was followed 
in Cracow, Leyden and London, only now to be 
abandoned by Tripler, Linde and Hampson, who 
have dispensed entirely with outside refrigerants 
and have made air and gases supply the cold for 
their own liquefaction. 

Dewar’s early apparatus of 1883 was designed sim- 
ply to liquefy oxygen in a glass tube for lecture pur- 
poses. The apparatus was arranged for projection 
of the gastube by the magic lantern. It is of interest 


(2 
o 
oe 
Z 
< 
a 
< 
< 
= 
a 
_ 
ma 


ine, 


zu 


's Maga 


? 


Courtesy of McClure 


in the Laboratory of the Royal Institution. 


f. Dewar 


Pro 


LIQUEFACTION OF GASES. 235 


as being the predecessor of the expensive apparatus 
since that period installed in the laboratories of: the 
Royal Institution. It will be seen that it differed very 
little from Olszewski’s apparatus of 1890, except that 
the receiver for the liquefied oxygen was a glass tube 
and that no means were provided for withdrawing 
the liquefied gas. . In any case, far too little was 
produced at a time to make it possible to pour it 
from vessel to vessel except on the most limited 
scale, if-at all. 

Prof. Dewar has been far from communicative on 
the subject of the liquefaction apparatus and meth- 
ods employed at the Royal Institution. They are 
based on the Pictet system of.successive cycles of 
cooling agents, one agent cooling the next, so as to 
secure several steps down the thermometric scale, the 
last being utilized for the gas to be liquefied. It is 
only very recently that a step forward has been made 
andthe self-intensive method adopted, and in the case 
of his hydrogen liquefactions superadded to the Pic- 
tet cycles. 

Now that the work has been done and air has 
been liquefied in large quantities by the expensive 
methods adopted and devised for the Royal Institu- 
tion work, it is with a feeling of sadness that we 
realize that the great quantities of liquefied ethylene 
which excited so much admiration were not. needed, 
and that, by the simple methods of Tripler, barrels of 
liquid air could have been made at ly nomi- 
nal expense. 

Referring to the cut, C is an iron oxygen reservoir 
within which is the oxygen gas compressed to. 150 
atmospheres. A is the regulating stopcock by which 


236 LIQUID AIR AND THE 


it is allowed to flow out of the reservoir as desired. 
The glass tube in which the. gas is liquefied is in- 
dicated by /, and the gas from C reaches it through 
a fine copper tube, 2. Dis a manometer to show the 


Dewar’s Early Oxygen Liquefaction Apparatus of 1883. 


pressure of the gas, and /is an air pump gauge to 
indicate the vacuum under which the refrigerant 
boils. 7 is the point of attachment of an air pump 
for producing this vacuum. 


LIQUEFACTION OF GASES. 237 


The gas liquefaction tube, 7, is surrounded by an- 
other tube, G, also of glass, in which is liquid ethy- 
lene, liquid nitrous oxide or solid carbon dioxide. 
These boil in the approximate vacuum produced by 
the air pump. It will be observed that a third 
vessel, K, surrounds G and #/, and that the exhaus- 
tion takes place from its bottom. Its top is hermeti- 
cally sealed, and holes at & permit the cold gas from 
G to flow down the annular space between G and K 
to keep the temperature low. 

When the pressure in the vessel, G, containing 
ethylene, is reduced to 25 millimeters of mercury, 
the temperature falls so low that oxygen liquefies 
when the manometer shows a pressure of 20 to 
30 atmospheres. If hquid nitrous oxide or solid 
carbon dioxide is used in G, then the pressure of 
the oxygen must be brought up to 80 to too 
atmospheres to compensate for the lower tem- 
perature. Or the lower temperature produced 
by the last two refrigerants may be supplemented by 
sudden release of pressure. The cock, 4, is adapted 
to effect this application of Cailletet’s principle. 

An ingenious suggestion is made by Dewar that 
solid nitrous oxide should be used instead of liquid 
nitrous oxide in order to prevent troublesome ebul- 
lition. 

He tried the specific gravity by evaporating -a 
measured volume of the liquid and determining its 
amount, and performed a number of experiments, 
naturally very much restricted in number and im- 
pressiveness by the exceedingly small quantity of 
liquid available and by its inclosure in a glass tube. 

_ Lately, however, more has been said of the Dewar 


238 LIQUID AIR AND THE 


processes of liquefaction, and details of a laboratory 
<pparatus of his for liquefying air and other gases 
have been made public. In England so much 
interest has been excited by the work of Linde and 
of Hampson, and the construction and theory of 
their apparatus have been so freely disclosed, that it 
seems time for the processes of the Royal Institu- 
tion laboratory to be made more public than they 
ever have been. Details, however, are still wanting. 

It follows, therefore, that there is no possibility of 
exactly describing the liquefaction apparatus in 
question. If, however, Pictet’s apparatus be taken 
as representing the type of a double cycle refrige- 
rating apparatus, the following give the data of its 
operation for the Dewar liquefactions of five years 
ago. 

The cooling agent of the first cycle was liquid 
nitrous oxide. This was compressed to about go at- 
mospheres and was evaporated in a condenser jacket 
so as to give a temperature of —go° C. (—130° F.) 
Through the inner condenser chamber liquid ethy- 
lene passed. This was under a pressure of over 120 
atmospheres, and was cooled by the evaporating 
nitrous oxide which surrounded it. The liquid 
ethylene, brought down to nearly —-90° C.(—130° F.), 
was passed into the jacket of a second condenser in 
which it was evaporated. The intensely cold liquid, 
cooled still more by its own evaporation, brought 
about a temperature of —145° C. (229° F.) 

A tube passed through the condenser jacket in 
which the ethylene evaporated, and through the tube 
oxygen, compressed to 50 atmospheres, flowed. It 
liquefied rapidly, and was drawn off as required. In 


LIQUEFACTION: OF GASES. 239 


drawing it off at this pressure, nine-tenths of it was 
lost. It was another illustration of the difficulty of 
coping with the mechanical troubles of too high 
pressure. We have had occasion more than once to 
allude to this trouble, and Dewar’s statement that he 
lost the greater part of his liquefied gas emphasizes 
what we have said about this feature of Pictet’s, 
Olszewski’s and Dewar’s early apparatus. A jet of 


IN 


Wn NE 
|" 


\[-— 


ayer N 
i BR < | 
Bl VCO Neale: h \s ff 
‘| U% By — \ - 
Us eh ye a aa 


<2 


Courtezy of McC lure’s Magazine. 
Machinery for Operating Liquefaction Apparatus, 
Royal Institution. 


liquid at 50 atmospheres is almost uncontrollable, 
and the action of a regulating cock is apt to 
involve some wasteful atomizing action upon the 
liquid. 

It was with this apparatus that oxygen and 
other gases were liquefied by Dewar in quantities 
almost unhoped for up to his time, and with it liquid 
air was prepared for the lectures which did so much 


240 LIQUID AIR AND THE 


to excite public attention on the subject of the lique- 
faction of gases. 

The apparatus was very large and heavy, and it 
involved the making of great quantities of ethylene 
by decomposing alcohol with concentrated  sul- 
phuric acid. This cost a great deal. Faraday’s old 
laboratory became the scene of operations which 
recalled a machine shop rather than a scientific 
workshop. 

Prof. George F. Barker, of the University of 
Pennsylvania, in visiting the scene of Dewar’s work, 
found almost as much to admire in the dozen cylin- 
ders of liquid ethylene as in the air and gas lique- 
factions which it accomplished. Commenting on 
the strange uses to which Faraday’s laboratory was 
put, Prof. Dewar told his friend that Faraday would 
have been the most delighted man in the whole 
kingdom had he been alive to see what was in course 
of accomplishment. The work was nothing but the 
following out of the path that Faraday pointed out, 
and in which he went as far as the knowledge of his 
time permitted. 

There is no difficulty in assenting to Prof. Dewar’s 
views thus expressed. 

Simpler apparatus was constructed later, and we 
illustrate Prof. Dewar’s small apparatus for effecting 
liquefactions without the use of pumps, reliance 
being placed on the use of cylinders of compressed 
gases. 

In the general view of the apparatus two com- 
pressed gas cylinders are seen. The one to the right 
contains compressed and liquid carbon dioxide, the 
one on the left contains compressed and gaseous 


LIQUEFACTION OF GASES. 241 


air or oxygen. The small cylinder above and 
in a central position contains the liquefaction appa- 


= TEL | Mm 
Tl] ) \ © 
! ‘( Jil 


M11 \\\ TASS 


Nl 


Dewar’s Small Gas Liquefaction 
Apparatus. 


ratus. It forms avery compact piece of apparatus. 
The next cut shows the condensing and liquefying 
portion of the apparatus in section. 


242 


LIQUID AIR AND THE 


The carbon dioxide gasifies as it escapes from 
the cylinder and enters the apparatus, passing in by 


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Section of Dewar’s Small Gas 


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Liquefaction Apparatus. . 


rated by the 


the inlet, &. It follows 
a coil of pipe which 
winds around the in- 
terior of the cylinder 
in parallel with a sec- 
ond similar pipe. This 
second pipe communi- 
cates by the inlet, 4, 
with the cylinder of 
compressed air or oxy- 
gen. In the sectional 
cut the carbon dioxide 
pipe is represented by 
the black circles, the 
air or oxygen pipe by 
the open ones. The 
carbon dioxide after 
passing through this 
coil escapes into the 
inner chamber of the 
apparatus and is regu- 
lated by a valve ope- 
hand 
wheel above C. 

The air or oxygen, 
after going through 
the outer coil, and get- 
ting a preliminary 


cooling from the carbon dioxide coil, enters the coil 
in the inner chamber indicated by the triple set of 


small 


open circles. 


Here 


it circulates around 


LIQUEFACTION OF GASES. 243 


through a great length of pipe and is further cooled 
by the expanding carbon dioxide, then goes through 
a third coil, intermediate between the outer coil and 
the inner chamber, and escapes, regulated by the 
valve, /. It liquefies and collects in G. 

In operation the carbon dioxide solidifies so that 
the gas is cooled by the solidified carbon dioxide gas. 

This apparatus was operated without exhaustion, 
the natural evaporation of the carbon dioxide giving 
a reduction of temperature to —79° C.(—110°2° F.) 
The tubing is of copper, to secure good heat conduc- 
tion and consequent rapid cooling. The rest of the 
refrigeration is due to the expansion of the oxygen. 
It is well to start with this gas compressed to: 150 
atmospheres and to utilize it down to a pressure of 
100 atmospheres. The liquid air or oxygen begins to 
drop in about fifteen minutes. The intensely cold 
expanded and unliquefied gas rises among the coils 
and cools them still more, so as to obtain a regen- 
erative action. The apparatus will make 100 cubic 
centimeters (about six cubic inches) of liquefied oxy- 
gen in an operation. - 

The spheroidal state has been somewhat fully 
treated in an earlier portion of this work. The orig- 
inal investigators of the phenomena of the liquefac- 
tion of gases never imagined how important a part it 
would play in facilitating their manipulation. Thanks 
to it, the hand can be immersed in liquid air. Liquid 
air rests quietly in atin dipper, and the length of time 
for which it remains in the open air in a common 
vessel is in many cases due to its taking the spher- 
oidal state. | 

But liquefied gases do evaporate rather rapidly in 


244 LIQUID AIR AND THE 


the air, and a great desideratum was some kind of a 
vessel that would hold them without the rapid loss 
experienced under ordinary conditions. Liquefied 
gases volatilize and disappear because they receive 
heat from surrounding objects and from the atmo- 
sphere. Early in his scientific work Dewar recog- 
nized that it might be possible to make this loss very 
much less, utilizing a vacuum as a non-conductor. 

The properties of a vacuum in intercepting the trans- 
mission of heat are utilized in what are knownas De- 
war's bulbs for holding liquefied gases. Air is often 
spoken of as a good insulator, and such it is. Abso- 
lutely quiet air is nearly as good an insulator as a 
\ vacuum. ~ : 

But the trouble is that air cannot be kept still, and 
if it is free to move, its mass, under the influence of 
heat, travels back and forth and carries heat with it, 
and thus by convection destroys the heat insulation 
of objects it is in contact with. Among objects in 
everyday use the incandescent lamp may be referred 
to as one in which a vacuum is utilized. A very con- 
siderable proportion of the efficiency of an incan- 
descent electric lamp is due to the vacuum within 
the bulb. The vacuum is not only useful in preserv- 
ing the carbon from combustion—a filling of the bulb 
with nitrogen gas would do this—but it keeps cold 
gas of any kind from coming in contact with the film 
and thereby cooling it. 

The incandescent lamp illustrates so admirably the 
heat insulating properties of a high vacuum that 
some experiments may here be cited which show the 
effect of filling the bulb of anincandescent lamp with 
various gases as contrasted with having it empty. 


LIQUEFACTION OF GASES. 245 


As the vacuum protects the film of an incandescent 
lamp from cooling, so does it protect a mass of lique- 
fied gas from heating. Dewar’s very elegant inven- 
tion is illustrated by an appeal to the other end of the 
thermometric scale from that occupied by liquid air. 

In the Philosophical Magazine of 1894 we read that 
Blenkroode filled three incandescent lamps with car- 
bon dioxide, coal gas and hydrogen respectively. 
A fourth lamp of the regular construction with a 
high vacuum existing in the bulb was added to the 
series, they were placed ona lighting circuit, and a 
piece of phosphorus was placed on top of each one. 
On passing a current through them, the vacuous 
lamp was the brightest, the presence of the gases 
chilled the other carbons, and the phosphorus was 
ignited in the following order: first, on the carbon 
dioxide lamp; second, on the coal gas lamp; third, 
on the hydrogen lamp, the regular lamp being the 
last on which the phosphorus ignited. The lamps 
varied in brightness in the same general order, the 
regular vacuous bulb lamp being by far the bright- 
est. This illustrates the utility of a vacuum as a heat 
insulator. 

In the case of the incandescent lamp the problem 
is to maintain the heat of an incandescent body in 
the vicinity of relatively cold objects. In the case of 
liquid air and gases the reverse has to be effected. 
A very cold body is to be prevented from receiving 
heat from surrounding matter. But, as is so often 
the case, opposites here come together, and the same 
means which will keep the film in the lamp from 
losing its heat will prevent liquid air from losing its 
cold, if such an expression may be allowed. 


246 LIQUID AIR AND THE 


A double-walled glass vessel in a measure pre- 
serves liquid gases from evaporation. The inclosed 
air acts as an insulator, but, by convection, carries 
heat from outer vessel to inner one. A triple-walled 
glass vessel is still better, as it gives two spaces filled 
with air. The earlier experimenters used double- 
walled vessels for another purpose. They found 
that liquid gases in a single glass vessel caused ice 
to rapidly form upon its outer surface, so that the 
contents were hidden, as the ice was white and 
opaque. They employed a double vessel and placed 
some drying agent between the two vessels, on the 
bottom of the outer one, to keep the air between 
them dry, so that no such ice could form. Wehave 
seen how in his early work Dewar used this device 
and others did the same. 

The Dewar vacuum bulb consists of a double or 
treble walled glass vessel, with the space or spaces 
between the vessels hermetically sealed and with a 
nearly perfect vacuum therein. The conditions in 
such a vessel are that the hquid in the interior one 
receives practically no heat. Glass is so poor a con- 
ductor that it conveys only slight traces by conduc- 
tion. The liquid receives none by contact with the 
air above it, as it is overlaid by the intensely cold gas 
evolved from itself. The vacuum surrounding it 
cuts off any heat from warm air coming against the 
sides of the containing vessel. Almost the only heat 
it can receive is that imparted by ether waves or, 
popularly speaking, by radiant heat. 

Ether waves of this description are such as we 
feel when we hold the hand near the bulb of an in- 
candescent lamp when hot and giving light. They 


LIQUEFACTION OF GASES. 247 


pass through glass with little loss. If the glass of 
the inner bulb, the one containing the liquid air or 
liquefied gas, were coated with some bright opaque 
substance that would reflect these waves, a further 
economy would be obviously effected. 

This was done for the glass bulbs by coating the 
surface of the inner bulb with silver. The bright 
metal reflected the ether waves, and a better effect 
in preserving the gas was the result. 

Then a still simpler treatment was discovered. A 
little mercury—a very little suffices—was left in the 
vacuous space outside the containing bulb. When 
liquid gas was put into the bulb, it chilled it and con- 
densed a mirror of mercury upon its outer surface, 
which reflected the heat waves. When the liquid 
gas was removed, the mercury disappeared again. 

Direct tests showed that a vacuum preserved the 
air about five times longer than would air. The fol- 
‘lowing figures are given: 


Relative Volumes of Liqueficd Gases Livaporating 
from Double Bulbs. 


Liquid oxygen, vacuum space, 170 volumes. 


ifs (<5 air cc 840 (<9 
fo ethylene vacuuin, |“ 56 : 
“6 7 air 66 230 See 66 


If the silvering process is applied, the influx of heat 
is reduced to about one-thirtieth of what it is with 
an air space, or, in round numbers, 34 per cent. 

Three dry air spaces, cne outside the other, only 
reduced the influx to 35 per cent. of what it was 
with a single space. 

It is. interesting to find that Prof. Dewar had 


248 LIQUID AIR AND THE 


used metallic vacuum vessels in 1873 in calorimetric 
experiments, which he describes in a paper read be- 
fore the Royal Society of Edinburgh, and printed in 


their 7ransactions, vol. xxvii. 


Courtesy of MceClure’s Magazine. 


Various Shapes and Modifications of Dewar Bulbs, 
and Liquefied Gas Containers. 


Various shapes can be given to the bulbs, and 
several are shown in the cut. The mercury silver- 
ing process is not always employed, as it may be de- 
sirable to have the liquid visible, and the deposition 


LIQUEFACTION OF GASES. 249 


of mercury on the glass cuts the liquid off from 
view. 
For some reason, vacuum. vessels deteriorate. The 


Sectional Views of Different Forms of 
Dewar’s Bulbs. 


vacuum cannot well be supposed to diminish, and 
no satisfactory reason can be given for the change. 

Prof. Dewar adopted, for the exhaustion of his 
vacuum vessels, the principle of 
the Torricellian vacuum combined 
with that of freezing mercury 
vapor. 

Suppose that the drawing repre- 
sents a glass bulb, A, for production 
of a vessel in which a Dewar vacu- 


. : Production of 
Meee sori inay bescaiied: 15 tO be’) pawar Vacuum. 


produced. The large bulb is the 

one which will eventually form the vessel. From the 
small bulb, W, the tube, 7, descends a distance of 
over 30 inches. 


250 LIQUID AIR AND THE 


To simplify the description, the single outer bulb 
alone is shown. The inner bulb is not represented 
in the drawing. It must be supplied by the reader’s 
imagination. 

The whole affair, tube and bulbs, is filled with 
mercury while inverted, exactly as in filling a 
barometer tube. By heating, or by some other 
manipulation, any air present may be expelled, for _ 
mercury, mobile as it seems, invariably holds bub- 
bles of air imprisoned when it is poured into a long 
tube. In filling barometers, several methods of get- 
ting rid of the air are employed, boiling the mercury 
being one of the best. Barometers thus treated are 
said to have “ boiled tubes.” 

The long tube with the large and small bulb, be- 
ing filled with mercury, is reversed in position, with 
its lower end immersed in a cistern of mercury. 
The mercury descends until it stands at a height 
of about 30 inches. By a little inclining of the 
tube, any mercury remaining in the bulbs can be 
made to enter the tube, or a little may be left there 
asa silvering agent. In the bulbs the Torricellian 
vacuum now exists. It would be a perfect and ab- 
solute vacuum except for the presence of mercury 
vapor. A blowpipe flame is applied at the outlet, 4, 
of the small bulb, the tube melts together, and the 
two bulbs are sameradl hermetically sealed. se trace 
of mercury vapor is still in them. 

The next operation is to chill the small buib by 
wiping it with a piece of cotton dipped in liquid air. 
As this touches the glass, the mercury vapor is 
frozen solid and is deposited on it and forms a mir- 
ror. This mercury is derived from the vapor which 


LIQUEFACTION OF GASES. BET 


exists in the bulbs. A sufhcient freezing removes 
almost every trace of vapor, and the mercury vapor 
is removed from the large and from the small bulb. 

Keeping the bulb cold with liquid air, the small 
neck between the bulbs is sealed off by the blowpipe 
flame, and the large bulb has now within it the most 
complete vacuum known. It is all but absolute. 
Some infinitesimal traces of mercury vapor are pres- 
ent. It responds to the most severe electrical tests 
for vacua. 

While a sufficiently long exposure of the small 
bulb to the absolute zero, were such attainable, 
might make the vacuum absolute, the difference 
between it and the Dewar vacuum would be infini- 
tesimal. 

The calculated pressure of mercury vapor at the 
temperature of melting ice is expressed by the deci- 
mal 0°000,126 millimeter of mercury. The reference 
is to a barometric column of mercury which has a nor- 
mal length of about 760 millimeters. Therefore, the 
above decimal expresses one six-millionth of an at- 
mosphere, certainly low enough for almost any 
purpose. But on lowering the temperature to 
—180° C. (—292° F.) by sponging the outer bulb 
with liquid air, the pressure of the mercury vapor 
falls to the figure 0°000,000,003 millimeter, or two 
and a half millionths of a millionth of an atmo- 
sphere. In powers of ten it would be expressed by 
25 x 10-* of an atmosphere. 

If a bulb of identical size were filled with mercury 
vapor at atmospheric pressure, it would, therefore, 
contain two and a half million million times as great 
a weight of mercury. Ifit were filled with air at 


252 LIQUID AIR AND THE 


atmospheric pressure, it would contain in round 
numbers one-fiftieth the above weight of air, or 
eighty thousand million times the weight of the mer- 
cury in the Dewar vacuum. 

Amazingly small as this quantity is, we can obtain 
some concrete idea of it from the population of the 
world. This may be taken at about one thousand 
millions. If then we had one thousand earths, and 
removed from them all of the human inhabitants 
except three, they would represent three-millionths 
of a millionth of the original population of our thou- 
sand worlds. 

Prof. Dewar seems amply justified in maintaining 
that the vacuum he produces is higher than any of 
which man had ever yet dreamed. 

The rate at which mercury is thus deposited has 
been investigated. All that was necessary was to 
apply the cooling process to a vacuum bulb contain- 
ing a globule of mercury. The latter supplied more 
mercury vapor as fast as, or nearly as fast as, it was 
deposited on the glass. The time of cooling was 
taken, and then the bulb was broken and the mercury 
weighed. The area over which the mercury was 
deposited being known, the data are reduced to mer- 
cury deposited on a given area in a given period. 

In ten minutes two milligrammes of mercury were 
deposited per square centimeter of surface. This 
gives a rather interesting figure. These two milli- 
grammes of mercury represent enough vapor to 
saturate in the Torriceilian vacuum no less than 
twenty liters or about twenty quarts capacity. A 
globe big enough to hold this quantity, if exhausted | 
by the Torricelli process, would contain just about 


LIQUEFACTION OF GASES. 253 


two milligrammes of mercury vapor, and ten min- 
utes’ cooling by liquid air sponging would remove 
this from the globe, 

Remembering that two milligrammes are equal to 
about three hundredths of one grain, and that twenty 
liters are equal to about twenty quarts, and that a 
twenty-liter globe would hold seven pails of water, 
we again have a concrete example of the effect of 
removing mercury vapor from a Torricellian vacu- 
um. It also gives us an idea of how near perfection 
a Torricellian vacuum is, and of what is gained by 
the freezing process applied to it. 

In scientific work one must always be on the 
watch for side issues: New and interesting facts 
constantly come out by accident, or are suggested in 
investigations having widély different ends in view. 
An interesting example occurs in the freezing of the 
mercury vapor in the bulbs we describe. 

The cut shows an apparatus designed to show the 
slowness with which mercury gas diffuses through a 
long, slender glass tube. Two bulbs, a large and a 
small one, are connected by a capillary tube. The 
latter in the experiment as executed by Dewar was 2 
millimeters (0°08 inch) in diameter and 50 millimeters 
(2inches) long. A little globule of mercury is in the 
smaller tube. A Torricellian vacuum is produced 
by the process already described, and the tubes are 
sealed up so as to maintain it within their interiors. 

The cotton wad, A, wet with liquid air, is apphed 
to the large bulb, and a mirror at once forms where 
the same is applied. All the mercury gas in the 
large globe deposits there, and, on touching another 
portion of the glass,no mirror shows itself. The 


254 LIQUID’ AIR AND “THE, 


mercury gas diffuses with such extreme slowness 
through the capillary tube that the latter for a while 
acts almost like a valve to shut off une communica- 
tion between the two bulbs. 

If now the bulbs are inclined so that a little mer- 
cury runs into the large one, then, on applying. the 
sponge elsewhere, a new mirror is at once formed. ° 

Such are the Dewar bulbs, one of the most valua- 


Dewar’s Experiment of Freezing Mercury 
Vapor in Connected Bulbs. 


ble of the mirror devices in connection with our sub- 
ject. These bulbs and the spheroidal state are what 
enable liquid air and gases to be handled almost as 
if they were so much water. Certainly, the ease of 
handling is comparable to the case of a volatile in- 
flammable liquid, such as benzene or ether. 

It is interesting to observe that sometimes the 
principle has been applied in a sense unconsciously. 
Thus, for the production of low temperatures, a ves- 


LIQUEFACTION OF GASES. 258 


sel is often surrounded by another one containing. a 
liquefied gas. The joint between the vessels is her- 
metically tight, and the liquefied gas in the space 
between is reduccd in temperature by the applica- 
tion of exhaustion, thus making it boil. 

Although this vacuum is applied simply to reduce 
temperature, one of its actions is to make the com- 
bination constitute approximately a Dewar vacuum 
vessel. 

We now pass to some determinations of data at 
low temperatures, giving as required illustrations of 
the apparatus employed by Dewar and his associates. 
Much ingenuity was required in carrying out some 
of these determinations, but they were made possible 
by the ample facilities for the production of liquid air 
and liquefied gases. Had the experimenters, relative- 
ly speaking, had such quantities of liquid air at their 
disposal as have been produced in New York city by 
Tripler, their tasks would have been still easier. 

The strength of metals and their rigidity are 
greatly modified by extreme cold. It is easy to 
show this in a crude way. Thus a spiral of soft 
metal, such as solder, an alloy of lead and tin, may 
be drawn out into a straight line by suspending a 
very small weight by it. But if cooled to the tem- 
perature of boiling oxygen or thereabout, it will 
support a weight fifteen or twenty times greater 
than before, without being drawn out of a spiral, and 
will spring like a watch spring. 

This experiment gives us an explanation of Tresca’s 
flow of solids. He found that, under great pressure 
long maintained, metals would flow like a very thick 
liquid, but very slowly. The soft metal, which is so 


250 LIQUID AIR AND THE 


easily straightened out, may be supposed at our 
everyday temperatures to exist in a state of semi or 
partial, perhaps much less than semi-fusion. The 
same becomes fully solid when cooled by liquid air. 

The same spiral will vibrate like a steel spring 
when intensely cold. At ordinary temperatures it is 
almost devoid of elasticity. 

A tuning fork or bell made of such metal will not 
ring at. ordinary temperatures, but when chilled the 
elasticity 1s increased so that tne metal becomes 
sonorous, the bell rings and the tuning fork sounds 
as if of steel or of bell metal. 

As an analogy at more familiar temperatures, we 
may refer to iron or glass. Either of these is rigid 
and elastic, but when heated becomes soft gradually, 
not melting at once, but passing through a slow 
change extending over many degrees range of tem- 
perature, and gradually approaching fluidity. We 
may assume that such metals as lead or tin at 
ordinary temperatures are undergoing a change of 
state, and are approaching fluidity. The only 
trouble with this view of the case is that, when such 
metals do melt, the melting is sudden, and is done 
within a very small range, perhaps less than a 
degree. 

If one of two tuning forks which are in perfect 
unison is chilled in liquid air, and the two are 
sounded, they are found to be no longer in unison. 
The colder one is of higher pitch than before, be- 
cause the intense cold has made it more elastic than 
it was. 

The difficulties of determining the strength of ma- 
terials when cooled to the liquid air temperatures 


LIQUEFACTION OF GASES. 257 


have been quite successfully overcome. The cut 
shows the general plan of apparatus used by Prof. 
Dewar for determining the tensile strength of mate- 
rials. As the piece should be of sufficient size to in- 
sure absence of flaws of any kind, 
the apparatus must be powerful. 
Metals increasing in tensile strength 
as cooled, the jaws of the apparatus 
which hold them have also to be 
cooled. Otherwise, the portions of 
the test piece near the jaws, being 
warmer than the rest, would be 
weaker than the rest, and the sam- 
ple would break there, and invali- 
date the test. 

In the cut, Disa silvered vacu- 
um vessel of liquid oxygen, C is the 
wire to be tested, 4 is a steel rod 
which runs to a set of multiplying 
levers which produce the breaking 
strain. At Bis an arrangement for 
determining the amount of exten- 
sion of the wire before breaking. 
When the test is to be made, the 
lower part of the apparatus is im- 
mersed in the liquefied gas, and the 
strain is applied. : 

If the heavy apparatus strikes enae for De- 
the vessel, the glass will break, and epee ue Tensile 

i , rength at Low 
an expensive piece of apparatus Temperatures. 
will be destroyed, and the liquefied 
gas will be lost. For this reason the apparatus has 
to be solidly constructed, so as to be secure from 


258 LIQUID AIR AND THE 


shaking or jarring under the heavy strains and from 
the sudden breaking of the sample under test. 

As a rule, Dewar used wires about one-tenth of 
an inch in diameter and two inches long. He gives 
the following table of his results. We quote it as 
published in the Zyvansactions of the Royal Institu- 
tion. The work was published in 1894. 


Breaking Stress of Metallic Wires tn Pounds, 0°098 
Inch Diameter, at 15° C. (59° FF.) and —182° C, 
(—295°6 J) 


eh Be —182° C. 

(59° F.) (—295°6° F.) 
Pteel (scotty were eee 420 700 
ITON eek cp teen eee ee 320 670 
(CODDEL Inhcenie ae es 200 300 
ISTASSS IL. beet ae orn 310 440 
Eras Vela 470 600 
Gro Te Dasete pee eta tay wae! 255 340 
DIWVGr ay at eeth. eae 330 420 


- The great increase of strength is due entirely to 
the reduction of temperature. When the wires are 
restored to their original temperature, the increase 
in strength disappears. 

The inhabitant of a world where the temperature 
approximated the absolute zero would have much 
stronger iron and steel with which to build his 
bridges, and he might make his watch springs out 
of pewter and his bells out of tin. 

With the same apparatus the breaking strain un- 
der longitudinal tension of test pieces of various cast 
metals was tried. The samples were all cast into 
shape. They were two inches long, they had hemi- 


LIQUEFACTION OF GASES. 259 


spherical ends one-half inch in diameter and a central 
cylindrical section two-tenths inch in diameter. This 
gave a shape somewhat like a dumbbell. 

The ends were received by cavities in the special 
steel end blocks in the testing machine, in which 
blocks hemispherical cavities were turned out to fit 
them. Although much discordance obtained among 
the results, the same general principle held as for 
tensile strength of wire. The chilled metals were 
stronger than at ordinary temperatures. The table 
of results we give here: 


Breaking Stress of Cast Metallic Test Pieces in Pounds, 
o'2 Inch Diameter, at 15° C. (59° F.) and —182° 
C. (—295°6° F.) 


pnd OF —182° C. 

Sorte) Ss 20540 aks) 
(ETN ak 2, SI AMIE fos Maat 200 390 
eats atic oe Fe 170 
TENA In eR eee a 35 26 
BYLGRCUL Vey ew yc. ee O 31 
ISISIUUL ee ence cre ae 60 30 
BVI OU eg ae ee toa: 61 30 
POL leet Most lets Gn « 300 645 
Fusible metal (Wood's) 140 450 


The abnormal results with zinc, bismuth and anti- 
mony are striking. These three metals are highly 
crystalline, and in this feature perhaps some expla- 
nation may lie hidden. 

The elongation results were not considered of any 
high degree of accuracy, but certain points were 
brought out by them. Thus tin and lead, at ordin- 
ary temperatures, elongate to the same extent be- 


260 LIQUID AIR AND THE 


fore breaking ; but after reduction of temperature, 
tin hardly stretches at all, while lead is as ductile as 
ever. Solder and fusible metal stretch less at the 
lower temperature. Stcel has its elasticity only 
slightly changed by refrigeration. Lead, tin, iron 
and ivory balls, when refrigerated, are increased in 
elasticity and bound higher than be- 
fore when dropped upon an iron an- 
vil. The cooled lead ball has a much 
smaller distortion produced where it 
strikes the anvil that it would were it 
uncooled. The area of the distortion 
surface is about one-ninth what it 
would be in a sphere of the same 
metal and size at ordinary tempera- 
Ibes, 

The cut shows how air, when lique- 
fied, can be preserved practically 
without evaporation, although at the 
expense of the evaporation of other 
liquefied air. Two vacuum tubes are 
used, placed one within the other, as 
shown in the cut.. The inner one 
connects with a tube, A, the outer 
one, C, with a tube, &. The sample 
of liquid air to be preserved intact is 
Apparatus for placed inthe inner vacuum tube. The 

Preserving = outer tube contains enough liquid air 
and Freezing | E F 

Liquid Air, to completely immerse the inner tube. 

By india rubber perforated stoppers, 
the necks of the vessels and of the tube, 4, are 
closed airtight, except for the passage through them 
of the tubes, A and &. All heat received is cut off 


LIQUEFACTION OF GASES. 261 


from the inner tube. The liquid air in the outer 
tube boils off slowly, and the liquid air in the inner 
tube is effectively preserved. If exhaustion be ap- 
plied to A and 4, the 
air in the inner tube 
freezes to a jelly-like 
mass. 

The apparatus 
shown in the cut was 
the apparatus used for 
determining latent 
heat of evaporation or 
the specific heat of a 
liquefied gas. The 
first requirement in 
thermic work is tc 
have a mass of the 
liquid under perfect 
control. It must be so 
placed that it will be 
permanent, and not 
evaporate. This con- 
dition is brought about 
by the arrangement 
shown in the cut, prac- 
tically a duplication of 
what has just been de- 
scribed, with some ad- 


Apparatus for Determining the 


ditional features. Latent Heat of Evaporation 
There is an outer Ae Specific Heat of Lique- 
vacuum vessel, G. In ed. Gases. 


it is placed the refrigerant, liquid air, oxygen or 
such liquefied gas as may be chosen. This vessel is 


262 LIQUID AIR AND THE 


corked, and a second vacuum vessel, C, is maintained 
concentric with it and immersed in the refrigerant. 

Latent heat of evaporation is determined by add- 
ing a known quantity of heat to the liquid and de- 
termining the quantity of gas evolved. Enough 
heat must be imparted to bring about evaporation, 
which heat may be imparted by dropping mercury 
into the liquid, as shown in the cut. Sometimes a 
piece of platinum, glass or silver is used. The 
weight of the substance added, its specific heat and 
its temperature being known, the quantity of heat 
imparted is calculated from these data. The. gas 
evolved is collected, and its weight being known, the 
data are given for determining the latent heat of 
gasification or of evaporation. The gas evolved is 
measured, and its weight is calculated from its 
known specific gravity. 

We now know the amount of heat added, and we 
know the amount of liquid which it has converted 
into gas. This gives the data for calculating the 
latent heat of evaporation. To determine the speci- 
fic heat, we have to ascertain the quantity of heat 
required to change the heat of a given amount of 
the liquid from one known temperature to another. 
These known temperatures are the boiling points at 
specified pressures. When such a pressure is pro- 
duced, the temperature of the boiling point at that 
pressure is reached. The following describes the exe- 
cution of a determination of latent heat of a liquefied 
gas: 

The capacity of the vacuum vessel, C, being known 
at given heights, it gives the quantity of liquid con- 
tained in it. 


LIQUEFACTION OF GASES. 263 


At Dis a three-way cock. When turned in one 
direction, it cuts off the tube, Z, and establishes com- 
munication between / and the vessel, C. In another 
position it cuts off the tube, / and connects & with 
the liquid gas vessel, C. The tube, /, leads to an air 
pump. The tube, /, being put in connection with 
C, exhaustion is applied until a vacuum of about one- 
half an inch of mercury is produced. This fixes a 
temperature for the liquid gas—the boiling tempera- 
ture at that pressure—which temperature is known. 
The stopcock, D, is turned so as to shut off F and 
bring £ into communication with C. 

The height of column is the vertical distance from 
the level of the mercury in the cistern to the level of 
that in the tube. Heat is now imparted by dropping 
mercury into C until the column of mercury in & 
sinks to the level of that in the cistern. 

Now heat enough has been imparted to raise the 
temperature of the liquid gas from its boiling point 
at one-half an inch pressure to its boiling point at 
atmospheric pressure, the latter being taken for 
each experiment from a standard barometer. The 
quantity of liquid gas thus raised in temperature 
being known, the data for determining specific heat 
are known. 

The mercury dropped into the liquefied gas in C 
needs particular management. It has a propensity 
for forming a stalagmite as it falls into the in- 
tensely cold liquid, and this must be prevented by 
dropping the mercury into different parts of the 
liquid. Another difficulty is the splashing of the 
liquid as the mercury falls into it. 

The latent heat of evaporation of liquid oxygen is 


264 LIQUID AIR AND THE 


about the same as the latent heat of melting of water, 
or 80 units, or the heat required to vaporize one part 
by weight of liquid oxygen would raise the heat of 
the same weight of water through 80° C. (144° F.) 

The behavior of a jet of gas issuing from a state of 
high compression may be studied by such apparatus 
as that shown in the next cuts. The apparatus was 
used by Dewar. In each piece is recognizable a 
vacuum tube with coil. 

In the first cut, Cis.a vacuum vessel: which cons 
tains a coil of tubing about 0°2 inch 
diameter. _ The vessel #in the vem 
periment is filled with a refrigerant 
such as liquid air. The tube is of 
silver or of copper, so as to be a 
good conductor of heat. At the 
end, A, is a minute aperture. 

If oxygen gas at a pressure of 
100 atmospheres is driven through 
the tube, escaping through the 
aperture, having previously been 
cooled in the tube, C, to a tem- 
perature of —79° C. (—110°2° F.), a 
liquid jet is just visible. The con- 
ditions here are not nearly so extreme as with Pictet 
in his experiment of 1877, in which a pressure of 270 
atmospheres was used. Dewar believes that one 
reason Pictet required so high a pressure was on 
account of his stopcock being massive and being 
outside of the refrigerating apparatus. It is also 
quite possible that Pictet used a higher Presse 
than was really needed. 

With air driven through the tube instead of oxy- 


LIQUEFACTION OF GASES, 265 


gen, 180 atmospheres are needed for liquefaction, and 
with a reduction of temperature to —115° C. (—175° 
F.) liquid air can be collected in vacuum vessel, D. 
This reduction is effected by applying exhaustion to 
the carbon dioxide in C. Or adhering to the natural 
evaporation temperature of carbon dioxide (—79° C., 
—110'2° F.), a pressure of 200 atmospheres at that 
temperature liquefies air. Naturally, Dewar found 
that the high pressure interfered with the collection 
of the hquid. An interesting point he speaks of is 
that the collection of liquid air can be increased by 
directing the jet against the tube above the hole. 
This to some extent brings out the self-intensive 
principle of Tripler’s, Linde’s and Hampson’s appa- 
ratus. By putting in a greater length of tube, as by 
making a coil, 5, the efficiency is increased. This is 
undoubtedly because the cold gas rising produces 
self-intensive action. An egg-shaped vessel acts in 
the same way. Dewar terms it the cold regenera- 
tive process, citing Coleman, Solvay and Linde as 
users of this principle. | 

The next cuts show modifications. In the first 
cut the pipe is coiled around an inner vacuum tube 
to get better insulation from heat. The inner 
tube is 9 inches long and 14 inches in diameter. 
Over the end of the metal tube a glass tube is 
slipped which stops the splashing about of and loss 
of the liquid air. It is evident that with such an ap- 
paratus the cold regeneratior would be very well 
carried out. The tube is coiled in a very restricted 
space, and the ascending excess of unliquefied air 
and of evaporated air at a very low temperature 
comes in contact under conditions of high efficiency 


266 LIQUID AIR AND THE 


with the metal coil. It is not surpris- 
ing to hear that with a pressure of 200 
atmospheres liquid air begins to collect 
in about seven minutes. The apparatus 
suggests one of Tripler’s early coils. 

Another disposition is shown in the 
last of the cuts, where the gas pipe is 
coiled disk fashion, leaving room in the 
center for introduction of a glass tube, C, 
in which samples can be placed which 
it is desired to subject to low tempera- 
ture. The glass cap to prevent splash- 
ing is seen in this cut also. 

These simple jet experiments are a 
good introduction to a study of the self-intensive 
apparatus, whose use has excited so much interest, 
both popular and scientific. 

Taking the critical temperature of hydrogen as 
31° C. absolute or —242° C. (—403°6° F.), it will be 
seen that the temperature of boiling air 
(—194° C., —317°2° F.) is well above it. 
—194° C. is 80° C. absolute, so that boil- 
ing air may be said to be two and one- 
half times hotter than liquid hydrogen 
at the critical point. It is not clear that 
this is a perfectly fair way of looking at 
it, however. ; 

Wroblewski and Olszewski had con- 
cluded that hydrogen had an abnormally 
low critical pressure. Wroblewski gave 
it a critical pressure of only 13°3 atmo- 
spheres, which is about one-fourth that 
of oxygen. The only trouble, therefore, 


a 
ny 


i 


PLT 


UL 


i 
I 
Vi 


(( 


LIQUEFACTION OF GASES. 267 


should be to get the temperature down. Dewar 
attempted to liquefy a mixture of hydrogen with 
two to five per cent. of air, and says that he obtained 
solid air together with a very volatile liquid of low 
density which he was not able to collect in a sepa- 
rate vessel. Olszewski longed for a gas intermediate 
in its critical point between air and hydrogen, to get 
what has aptly been termed static hydrogen, or 
hydrogen liquefied in quantity. 

Accepting Dewar’s view that hydrogen at 80° C, 
absolute is two and one-half times as hot as it is at its 
critical temperature, and taking air at two and one- 
half times its critical temperature, we should find 
that the liquefaction of hydrogen from the initial 
temperature of boiling air wou!d be equivalent to 
the liquefaction of air from 60° C. (140° F.) or 333° C. 
absolute. This figureis thus reached: The critical 
temperature of air is taken at —140° C. (—220° F.) 
This reduces to 273—140 = 133° C. absolute. Two 
and one-half times 133 are 333, which is the absolute 
temperature, two and one-half times greater than 
—140° C. (—220° F.), and 333° C. absolute is equal to 
333—273 — 60° C. (140° F.) Its possible to liquefy 
air by the jet method from a still higher temperature 
than this. Dewar found that starting with air at 
an initial temperature equal to that of boiling water, 
he could liquefy air in seven minutes by the pro- 
cesses described. 

It would, therefore, seem as if hydrogen at the 
initial temperature of the boiling point of air should 
be liquefiable by the process which liquefied air from 
the initial temperature of boiling water. 

Hydrogen was cooled a few degrees below this 


268 LIQUID AIR AND THE 


point, to —200° C. (—328° F.) and was driven 
through a fine aperture under a pressure of 140 at- 
mospheres, but without result. A very httle oxygen, 
some few per cent., was mixed with the hydrogen, 
and a liquid was obtained which contained hydrogen 
in solution, but was principally oxygen. It gave off 
hydrogen and oxygen in explosive proportions. 

The experiment was now tried with the regenera- 
tive coil in the first figure of the cuts, page 264. The 
escaping gas cooled the coil, 4, and the regeneration 
brought about, apparently, a liquefaction of hydro- 
gen. A liquid jet could be seen after the circulation 
had continued for a few minutes, and a liquid in 
rapid rotation in the bottom of the vacuum tube, D, 
could be discerned. 

The difficulty of recognizing a volatile, highly 
mobile liquid, formed under such conditions, and so 
very evanescent in duration, cannot be too strongly 
insisted on. A stream of gas was rushing out of an 
orifice at fifty times the pressure of steam in an 
ordinary boiler, a portion of it liquefied for a very 
brief period, and then gasified. The violence of the 
operation would at least tend to confuse quiet obser- 
vation. 

Dewar states that, owing to the low specific 
gravity of the liquid and the rapid current of gas, 
the latter impelled by a pressure of 140 atmospheres, 


or about one ton pressure to the square inch, none © 


of the liquid in question accumulated. “Static hy- 
drogen”’ was almost produced, the liquefaction was 
destined to be soon accomplished, and in its proper 
place (page 280) will be found described. | 
The jet system of cooling by impingement has in 


‘ 
— 


LIQUEFACTION OF GASES. 269 


several places been alluded to. Cailletet in early 
days, unable to conceive of the possibility of using 
liquefied gases by the gallon as refrigerants, sug- 
gested the use of ethylene jets for cooling. It was 
the chalumeau du froid, or cold blast blowpipe, of 
Thilorier. 

Dewar tried his hydrogen jet as a refrigerant. 
Liquid air and liquid oxygen were successively 
placed in the bottom of the vacuum tube, VD, so as to 
cover the jet. In a few minutes, in each of the two 
cases, about 50 cubic centimeters (3 cubic inches) of 
the air and oxygen respectively were solidified into 
hard, white solids like avalanche snow. 

When the air was solidified by evaporation zz 
vacuo, the product was a jelly; but in the experiment 
just described, the cold was so much more intense 
that oxygen-ice and air-ice were produced. The 
solid oxygen had the characteristic. bluish color of 
the liquid oxygen. Light reflected from it showed 
in the spectroscope the characteristic bands shown 
by light transmitted through liquid oxygen. 

In the description of these experiments the Joule- 
Thomson effect (page 297) was taken no cognizance 
of. All was treated by Dewar as examples of cold 
regeneration, not of internal intensification. There 
is a very open question as to how important a role 
the Joule-T homson effect really plays in these cases. 
Hydrogen, it will be remembered, does not present 
mie-etiect, but the reverse. On escape trom; pres- 
sure under what may be termed Joule-Thomson con- 
ditions—conditions adapted to bring out the Joule- 
Thomson effect—its temperature rises. In the ex- 
periment, as described by Prof. Dewar, the bydro- 


270 LIQUID AIR AND THE 


gen liquefaction is described as due to simple cold 
regeneration. It would seem as if it was ren- 
dered less powerful by the heating, or, as it may 
be termed, by the negative Joule-Thomson effect 
found to exist with hydrogen, unless, as Dr. Onnes 


Dewar’s Hydrogen Jet Apparatus. 


believes, the negative effect is reversed at low tem- 
perature. 

The illustration shows the general scheme of 
Dewar’s more elaborate apparatus for cooling hydro- 
gen by its own expansion. A is a cylinder charged 
with hydrogen under high pressure. A#and C are 


LIQUEFACTION: OF. GASES. agit 


vacuum vessels, each inclosing a coil of the gas de- 
livery pipe. #& contained solid or lquid carbon 
dioxide. The vessel was closed and its interior kept 
under exhaustion so as to lower the temperature. C 
contained liquid air. J is the self-intensive coil ter- 
minating at G, where there is a pinhole aperture. 
The first evidence of the intense cold in the freezing 
of air to a hard solid led to the erection of a very 
powerful apparatus, by means of which the liquefac- 
tion of hydrogen was effected. 

This liquefaction is the last great achievement in 
the field we are studying. The subject, therefore, 
will be dropped for a few pages in order to preserve 
the chronological relations. 

Air is always contaminated with carbon dioxide 
gas, and the small quantity normally present, four 
parts in ten thousand, which, however is subject to 
considerable variation, suffices to produce a turbid- 
ity in the liquefied product. Oxygen made as it 
usually is, from potassium chlorate by ignition, con- 
tains traces of chlorine, and this tends to produce 
turbidity in the oxygen when liquefied. 

There are cases where in a mixture of gases one 
constituent liquefies while the other solidifies. It is 
possible to purify a gas from some mixtures by 
liquefying the mixture and filtering. In lecture ex- 
periments with hquid air, it is usual to filter the 
liquid in order to procure transparent samples to 
show the faint blue color. 

Gases, however, sometimes dissolve in other lique- 
fied gases, just as they do in water. Soda water isa 
solution of carbon dioxide gasin water. Thus liquid 
air dissolves hydrogen. It is found that as much as 


272 LIQUID AIR AND THE 


twenty volumes of gaseous hydrogen may be dis- 
solved in one hundred volumes of liquid air. This, 
however, is not a large quantity. It must be remem- 
bered that the one hundred volumes of liquid air 
give when gasified about eighty thousand volumes 
of gaseous or ordinary air such as we breathe. 

We illustrate the apparatus with which the experi- 
ments touching on this solubility of gases in liquid 
air were made at the Royal Institution by Dewar. 
B represents a cylindrical empty vessel of glass, 
something like a pipette in shape. It fits into a 
vacuum vessel, the joint between the opening of 
the vacuum vessel and the neck of the tube, BZ, be- 
ing made tight by perforated stoppers. Through 
the central aperture of the cork or india rubber 
stopper, which is large, a branch tube passes, and 
through the center of this the neck of B, which is a 
capillary tube, passes. The whole is made air-tight 
by a perforated cork or india rubber stopper in the 
branch tube, through an aperture in which stopper 
this tube passes. A flask, A, contains liquid air, and 
a siphon, /#, is so arranged that it delivers liquid air 
into the vacuum vessel, and keeps its level such that 
the tube, &, is constantly covered with liquid air. 
An air pump is connected above the neck of the 
vacuum vessel and keepsa high degree of exhaustion 
over the liquid air in K. The tube, A, from the 
flask, A, enters the vacuum vessel through the second 
aperture in the rubber stopper which closes the neck 
of the vessel in question. 

The tube, /, leads to a gasholder full of air. This 
gasholder is graduated so that the air which it de- 
livers is measured. Under the influence of the in- 


— 


LIQUEFACTION OF GASES. 273 


tense cold, air liquefies in the tube, 8, coming from 
the gasholder and passing through the tubes, C and 
D, the lower one, C, charged with potassium hydrate, 
the upper one, JY, with pumice stone saturated with 
sulphuric acid. Thus the air before it reaches 2 is 
thoroughly purified. 


SS 


SSS PUMICE 42s 
SS =. }1 3004S 


TO EXHAUST PUMP, | 


Dewar’s Apparatus for the Examination of the Least 
Condensible Constituents of Air. 


After forty minutes’ operation with pure air the 
body of the tube, B, and the cool part of the capillary 
tube were filled with liquid, showing that everything 
delivered from the gasholder was liquefiable. From 
two anda half to three feet of air were used in each 
experiment. The capillary tube was so small and 


274 LIQUID AIK. AND Gre 


long that if only one volume out of 180,000 volumes 
of gaseous air had been unliquefied, it could have 
been detected. The first experiment showed com- 
plete condensation or liquefaction. 

To the gasholder of 283 liters capacity ( o cubic 
feet) and holding that quantity of air, one-half a liter 
of hydrogen was added, which was in the propor- 
tion of less than one volume in five hundred. The 
experiment was repeated. 

The tube, 2, would not fill; only four-fifths of its 
volume was occupied by liquid, the other fifth was 
occupied by gas. 

At £is a stopcock of the variety termed three- 
way. Turned in one direction, it connects B with J/, 
C, and D, the air or gas supply. Turned in another 
direction, it connects & with the tube, / Hitherto 
it had been turned so as to connect the air supply 
with B. Now it was turned so as to shut off the air 
and connect 2 with the tube, 7 The temperature 
was allowed to rise a little, so that the gas from the 
upper portions of & bubbled up into /. The lat- 
ter was originally filled with water. Its upper end, 
not visible within the limits of the cut, was closed. 

The gas thus collected was tested and proved to 
be principally hydrogen. 

Next air containing one volume of hydrogen in 
one thousand volumes of air was tried, and a very 
little hydrogen remained uncondensed. Finally, one 
volume of hydrogen was added to ten thousand vol- 
umes of air, and this liquefied completely. 

Therefore, one volume of gaseous hydrogen in one 
thousand volumes of gaseous air can be almost com- 
pletely liquefied. In the experiment, eighty thou- 


LIQUEFACTION OF GASES. 275 


sand cubic centimeters of air were condensed to 
about one hundred cubic centimeters of liquid air, 
and dissolved eighty cubic centimeters of gaseous 
hydrogen. In other. words, air liquefied at atmo- 
spheric pressure dissolves about eight-tenths of its 
liquid volume of gaseous hydrogen. 

The apparatus just described was used for a most 
interesting piece of work, the separation of helium 
from the gas evolved from the water of the King’s 
Well at Bath, England. This element, first discov- 
ered by spectroscopic observation in the sun and 
named from that fact, was not known to exist upon 
the earth. But some minerals were found to con- 
tain it in small quantities, and the gas from the Bath 
spring gave its spectrum. A good object for experi- 
ment was desired, which would show how applicable 
the method just described was for separation from 
each other of gases of varying degrees of ease of 
liquefaction. 

The gas from the Bath spring contains a little over 
one-thousandth of its volume of helium (00012 vol.) 
The gasholder was filled with the gas, and the experi- 
ment just described was repeated. The tube, B, col- 
lected a liquid, not clear like liquid air, but turbid and 
yellowish brown. The color was found to be due to 
organic matter, probably of the petroleum family. 
Tested with nitric acid, it gave the familiar odor of 
nitro-benzoie or of artificial oil of bitter almonds. 
This odor resembles that of the kernels of peach pits. 
It is sometimes used for perfuming soap. 

After an hour some 20 cubic centimeters of gas 
had collected in B above the liquefied gas. Seventy 
liters of gas were liquefied. 


270 LIQUID AIR AND THE 


The liquid in the tube was nitrogen. By letting 
the temperature rise, after properly turning the stop- 
cock, £, the gas along with some nitrogen was col- 
lected in‘the tube, #. ~The sample ‘collected was 
about one-half nitrogen and one-half helium. 

The experiment was extremely satisfactory as 
showing the practicability of using this liquefaction 
method for separating traces of less condensible gases 
from those which are more so. As Prof. Dewar 
observes, a regular gas liquefaction apparatus could 
be installed at Bath and made to produce any quan- 
tity of helium, were there any demand for it. 

In this class of experiment we see fractional con- 
densation, long since applied in distillatory processes, 
applied to gases. Itis an interesting subjection of 
the most elusive substances to processes hitherto 
only applied to ordinary liquids. 

A rather interesting demonstration of the action of 
mixed gases when liquefied in presence of each other 
was afforded by the liquefaction of oxygen in the 
presence of an excess of hydrogen. The liquid, as 
we have seen, could contain but little hydrogen. Yet 
the gas given off by it contained so much that it was 
explosive. In the evaporation, naturally a much 
larger relative proportion of hydrogen evaporated 
than of oxygen, so that the gas contained perhaps 
over one-half its volume of hydrogen, while the liquid, 
as we have seen, could contain but a little more than 
a trace dissolved. 

One of the recent triumphs of chemistry was the 
isolation of fluorine. For generations of chemists it 
had proved an element which could not be separated 
from its compounds. It has most intense affinities 


LIQUEFACTION OF GASES. 2/7 


for other elements, and attacks glass with much 
energy. Moissan, a French chemist, succeeded in 
separating it in the elemental state. In 1897 Mois- 
san and Dewar, working together, liquefied it. 

From theoretical considerations it appeared that 
fluorine should be more difficultly liquefiable than 
chlorine. Thus boron fluoride and silicon fluoride 
are gases, the corresponding chlorides are liquids. 
The same holds with many organic compounds— 
those containing chlorine being liquid and those con- 
taining fluorine being gaseous. This, obviously 
enough, was taken as indicating that fluorine was 
more difficult to liquefy than chlorine. 

The experimenters made fluorine by electrolyzing 
a solution of potassium fluoride in hydrofluoric acid. 
The gaseous fluorine evolved was passed through a 
platinum condenser tube which was cooled by solid 
carbon dioxide mixed with ether. This was intended 
to condense all impurities. It passed through another 
platinum vessel filled with perfectly dry sodium flu- 
oride and then into the liquefaction vessel. 

One of the great troubles of fluorine, as a subject 
for experiment, is that it attacks glass. For this rea- 
son platinum vessels are used for accurate work with 
it and its compounds. Lead stills and flasks are used 
for rough work, and the natural mineral fluorspar 
has even been suggested as a material for vessels. 

The lquefaction vessel was a glass capsule into 
whose upper part a platinum tube was soldered. 

Vhe tube from the fluorine evolution and _ purifica- 
tion apparatus entered the outer tube and passed 
down the annular space into the glass cylinder or 
capsule. The latter was immersed in liquid oxygen, 


278 LIQUID AIR AND THE 


which, boiling at atmospheric pressure, gave a tem- 
perature of —183° C. (—2y7°4° F.) The glass was 
not attacked at this low temperature, and the fluor- ~ 
ine did not liquefy. Exhaustion was now applied 
to the oxygen, and the reduction of pressure reduced 
the temperature to about —187° C. (—304°6° F.) A 
dew of liquefied fluorine began to appear upon the 
olass. 

In the first experiments the platinum tube leading 
out of the vessel had no cock. Upon closing it with 
the finger, fluorine at once began to collect in the 
glass capsule, which rapidly became partly filled 
withit. It was a clear, very mobile liquid of yellow 
color. The intensity of the color was stated to be 
equal to that which would be given by a column of 
gaseous fluorine one meter long. 

The liquid was so cold as to have little chemical 
power left. A number of substances were tried. 
Silicon, boron, carbon, sulphur, phosphorus and 
iron reduced in hydrogen could, after cooling with 
liquid oxygen, be dropped into it without any reac- 
tion. Ordinarily, fluorine would attack them vio- 
lently. At the temperature of —180° C. (—292° F.) 
it attacked benzene and turpentine. It could not 
separate iodine from potassium iodide. Hydrogen 
burned upon the surface of the liquid when caused 
to impinge thereon. 

It was cooled to —210° C. (—346° F.) by boiling 
liquid air, in hopes that it would solidify, but it re- 
mained liquid. By accident, some air got into the 
capsule of liquid fluorine. It liquefied and floated 
upon it, a colorless or faint blue liquid upon the 
pale yellow fluorine. But, by passing a current of 


LIQUEFACTION OF GASES. 279 


fluorine through liquid air, a flocculent precipitate 
formed. This was filtered out, and on heating ex- 
ploded with great violence. In a subsequent experi- 
ment the same layer of fluorine under the liquid 
oxygen just described was formed by passing 
fluorine to the bottom of a vessel of liquid oxygen. 
Evidences were found that liquid oxygen would 
dissolve it under certain conditions, the fluorine be- 
ing admitted, not to the bottom, but to the surface 
of liquid oxygen. The subject remains obscure. 

The specific gravity was determined by placing 
in it different substances of known specific gravity 
and observing which ones floated and which ones 
sank. Ebonite, caoutchouc, wood, amber and methyl 
oxalate were taken. The pieces were placed in the 
empty tube, and fluorine was liquefied in it. Wood, 
caoutchouc and ebonite floated, the methyl oxalate 
sank, and amber was almost indifferent. This gave 
it the same specific gravity approximately as that of 
amber, Or 1°14. 

The amber could only be seen with difficulty, so 
that the refractive index of liquid fluorine is almost 
the same as that of amber. 

On cooling it from —187° C. (—304'6° F.) to 
—z210° C. (—346° F.), it diminished one-eleventh in 
volume. It possessed no magnetic features as far as 
tested. : 

Its capillarity is less than that of liquid oxygen. 
The relative heights to which it and other liquids 
rise in a capillary tube were determined, with the 
following results : . 

iquidsiioriners635 4Alcohol 4... 2.4: 140 
eiaudwoxy Tent eco ater. Bir oni. 6 220 


280 LIQUID AIR ‘AND THE 


Water, therefore, rose about seven times as high as 
fluorine. | 

May 10, 1898, is one of the classic dates in our 
subject, for it was on this day that Dewar liquefied 
hydrogen, and obtained it in quantity as a “static 
liquid.” ; 

A very powerful train of liquefying apparatus had 
been set up in the Royal Institution, its erection ex- 
tending over a year’s time. It weighed two tons 
and contained 30,000 feet of piping. 

Hydrogen was cooled to —205° C. (—337° F.) ata 
pressure of one hundred and eighty atmospheres. 
The gas was allowed to escape continuously from 
the nozzle of a coil of pipe, at the rate of ten or fif- 
teen cubic feet a minute. When it is stated that an 
ordinary gas burner burns about six cubic feet per 
hour, it will be seen that hydrogen was used most 
profusely. The jet issued into a doubly silvered 
vacuum vessel, surrounded by another vessel, the 
intervening space being kept at —200° C. (—328° F.) 
Soon drops of hydrogen began to appear, and in 
five minutes twenty cubic centimeters had collected. 
The goal was won. Static hydrogen lay quietly in 
a vessel. 

The jet then closed with frozen impurities from the 
hydrogen. One per cent. of the gas had been col- 
lected in the liquid form. 

A small glass bulb was weighed in the liquid and 
gave a specific gravity of o7o8—an amazingly low 
figure. The end of along glass tube sealed at the 
bottom was placed in it, and at once became filled 
with solid air. Liquid oxygen was placed in a tube 
and immersed in it, when a blue solid was produced 


LIQUEFACTION OF GASES. 281 


from the frozen liquid. It was solid oxygen, or 
oxygen ice. 

A glass tube closed at its upper end was placed in 
a vertical position with its lower open end immersed 
in a vessel of mercury. It was so arranged that its 
upper end could be cooled by liquid hydrogen. On 
doing so, the mercury rose in the tube as the air 
solidified, until it stood within a minute fraction of 
an inch of the height of the barometric column. 

If liquid hydrogen were placed in a double-walled 
non-exhausted vessel, it froze the air in the inter- 
space solid, and the inner vessel became coated with 
a hoar frost or coating of solid air, literally of air-ice. 
The liquid hydrogen manufactured its own Dewar’s 
bulb. . 

A metal rod dipped in it became so cold that, on 
removal, liquid air fell from it in drops, liquefied by 
the cold of the rod due to its immersion in the liquid 
hydrogen. 

A sample of the helium obtained by Dewar from 
the gas of the Bath spring (page 275) was at hand in 
a sealed bulb with a narrow tube attached toit. The 
tube was dipped into the liquid. hydrogen. Liquid 
helium formed in it as a distinctly visible liquid. 

As a control experiment, the same tube was put 
into boiling air and no liquid formed. This showed 
that the cold of boiling air was insufficient to pro- 
duce a liquid from it; the liquid hydrogen gave a 
degree of cold sufficient to do it. 

The boiling point of the liquid hydrogen in the 
first experiments was determined by a platinum re- 
sistance thermometer. At 0° C. (32° F.) this hada 
resistance of 5°3 ohms. In the liquid hydrogen the 


282 LIQUID AIR AND THE 


resistance fell too'1 ohm. From the observation the 
temperatures of —-238°2° C. (—396°76° F.), —238°9° C. 
(—398° F.) and —237° C. (—394'6° F.) were calcu- 
lated on slightly differing bases. These temperatures 
are about 8° C. (14:4° F.) higher than Wroblewski’s 
calculated temperature of boiling hydrogen, and 
5° C. (9° F.) higher than that given by Olszewski’s 
calculation. 

In later experiments the following results were ob- 
tained: The resistance of the platinum wire resist- 
ance thermometer sank from 5°338 ohms at o° C. 
(32° F.) to o129 ohm at the boiling point of hydro- 
gen. This gave the boiling point as —238° C. 
(—-396°4° F.) The resistance of the platinum wire in 
liquid oxygen was eleven times that of its resistance 
in liquid hydrogen, both at atmospheric pressure. At 
its boiling point the pressure of air, which is solid at 
that temperature, is but o'002 millimeter of mercury. 
This is one three hundred and eighty thousandth 
of the normal pressure. The vapor density of hy- 
drogen at the temperature of its boiling point is 
eight times greater than at ordinary temperatures, 
or about one-half as heavy as air at ordinary temper- 
atures. 

The critical temperature is about 50° C. absolute 
(90° F. absolute) and the critical pressure is less than 
fifteen atmospheres. The latent heat is about two- 
fifths that of oxygen. The application of a vacuum 
to liquid hydrogen, therefore, cannot lower its tem- 
perature very much, compared with the cases of 
other gases. 

An approximate determination of the density was 
made by measuring off ten cubic centimeters of the 


LIQUEFACTION OF GASES. 283 


liquid, and collecting and measuring the hydrogen 
gas from it. The result was 0o°07—not far from that 
obtained> by weighing the glass bulb in ‘it. It is 
about one-sixth that of liquefied marsh gas (0°41). 

The light, evanescent liquid is, nevertheless, per- 
fectly visible, has a defined meniscus, and can be 
readily manipulated in vacuum vessels. 

The atomic volume at the temperature of its 
epullition ) is’ 14°3). (Oxygen—=13°7; nitrogen=-16'6). 
The gaseous hydrogen at this temperature has a 
Secilic’ Sravity, O1.0°55 (air—=1)."> The ratio of the 
specific gravity of the gas, compared to that of the 
liquid at the ebullition point, is as 1: 100 (oxy- 
gen—1I: 255). 

The specific heat of gaseous hydrogen and of 
hydrogen occluded in palladium is 3°4; of liquid 
hydrogen, 6:4. The specific heat of the liquid, per 
unit volume, is 0°5, or about that of liquid air. 

Liquid hydrogen affords a rapid means of obtain- 
ing one of the nearest approaches to a perfect 
vacuum which man can produce. We have just 
seen that air is solidified by the cold of liquid hydro- 
gen. A tube is filled with air and sealed. The end 
of the tube is placed in liquid hydrogen. With sur- 
prising rapidity the air in the tube solidifies and 
collects in the lower end where immersed in the 
liquid, and a vacuum, almost perfect, is formed in 
the rest of the tube. An immersion of one minute 
in never exceeded. The tube, while its end is still 
immersed, is softened with the blowpipe flame above 
the hydrogen vessel, or as near where it emerges 
therefrom as possible, and under the effect of atmo- 
spheric pressure it closes and is sealed off. Thus a 


284 LIQUID AIR AND THE 


vacuum tube is produced without pump or other 
apparatus of similar function. The process is so 
simple and efficacious that it would seem to give a 
suggestion for the production of other vacuous ves- 
sels, such as incandescent lamps. A more easily 
solidified gas could be substituted for air, and liquid 
air could take the place of hydrogen. Sir William 
Crookes, celebrated for his work on high vacua, 
from whom the vacuum tubes used in high vacua 
experiments are named, examined these tubes. He 
found that a higher vacuum was produced than he 
was in the habit of getting in his own tubes, after 
several hours’ work with the mercury pump. 

On spectroscopic examination, the spectrum of 
carbon and of hydrogen was obtained. Neon and 
helium lines were also found. The carbon spectrum 
is attributed to carbonates in the glass. 

An actual trial was made to determine what low- 
ering of temperature would result from reducing the 
pressure under which the hydrogen boiled. As 
has been already stated, no great reduction was 
anticipated; “not over 9° Co (i625 "P.) indes 
an exhaustion of one inch of mercury, very 
little lowering was effected. The extent of reduc- 
tion due to the partial vacuum only amounted to 
1° C.(1°8° F.) Possibly the platinum thcrmometer 
did not give the right result; possibly the connec- 
tions conducted heat; possibly the resistance curve 
of platinum cannot be relied on at such excessively 
low temperatures. 

With the liquefaction of hydrogen in bulk the 
story of the liquefaction of gases culminates. The 
date is but a few months before the period in which 


LIQUEFACTION OF GASES. 285 


this book was written. It seems a most appropriate 
time in which to put together the long chronicle of 
a hundred years’ efforts to liquefy gases, and whose 
final triumphs are no less Tripler’s great buckets of 
liquid air, made in the city of New York, and sent 
off hundreds of miles by rail, than they are the few 
teaspoontuls of liquid hydrogen liquefied by Dewar 
and his colleagues in the Royal Institution in Lon- 
don. 

Hydrogen has been treated as a metal. In its 
liquefaction many expected that a metallic liquid 
like mercury would result. But the product was 
not in the least metallic, and was a non-conductor 
of electricity, so that a much mooted question as to 
the nature of hydrogen is at last settled. 


LIQUEFACTION OF GASES. 287 


CTEAR TER tl: 
CHARLES E. TRIPLER. 


The life of Charles E. Tripler—His early experiments with 
gas motors—Mechanical difficulties encountered—His 
electrical experiments—Chemistry—His work in fine art 
—Exhibition of his pairitings—Return to the investiga- 
tion of compressed gases—Liquefaction of air—He en- 
deavors to utilize the low grade heat of the universe— 
Simplicity of his apparatus—The plant—The compressor 
—General plan of operations—Capacity of his plant— 

How he transports liquid air—His lectures—Raoul Pictet 
in Charles E. Tripler’s laboratory. 


Charles E. Tripler was born in New York, August 
10, 1849. From his early years he showed a great 
fondness for mechanics and experimenting, which 
fondness soon developed into practical work. Inthe 
early seventies his attention was directed toward 
the production of a motor to be driven by gas. He 
experimented.on an engine driven by ammonia. His 
work was different from that of others in one im- 
portant respect. The endeavor had been to actuate 
an engine by the pressure of ammoniacal gas, and to 
reduce its pressure by dissolving it in water. 

This process Tripler wished to avoid. He desired 
to work the ammoniacal gas in a continuous cycle 
without having resource to solution. Gasolene and 
naphtha were next tried, much trouble being expe- 
rienced in those early days with the joints in the 


288 LIQUID AIR AND THE 


apparatus, high pressure work in engineering having 
greatly developed during the last twenty-five years. 
One of the objects was to produce a motor for use 
on street cars. 

Electricity and chemistry were now (1873-76) 
taken up. Edison was at the same time engaged on 
electrical problems, and Tripler left the field and 
took up art. 

An artist by nature, he painted and exhibited 
paintings, and left his mechanical and scientific work 
almost untouched for a few years. 

About 1884 he worked on gold extraction and 
amalgamation and then returned to his first love 
and experimented with gases of many kinds, ethyl 
chloride, methyl chloride, and at last with carbon 
dioxide. During these researches he discovered the 
principle on which his work on the liquefaction of 
air has been based. 

Nitrous oxide was the next gas to be experimented 
with, and an explosion brought about during the 
generation of the gas nearly cost the investigator his 
life. His work, being at high pressure, and with 
many gases, has always been attended with peril, and 
the wholesale manipulation of liquid air is far from 
safe, irrespective of the question of pressure and dan- 
ger of explosion. All sorts of gases were made and 
liquefied, and about 1891 air was liquefied. 

The key to his life’s work has been the effort to 
use gases for motive power, Carnot’s cycle giving 
the clew to what he has desired to accomplish. 

He desired to utilize the heat of the sun. If the first 
chapters of this book have been followed out to their 
conclusions, it will be seen that the utilization of the 


LIQUEFACTION OF GASES. 289 


low grade heat energy of the universe, in accordance 
with Clerk Maxwell’s dream, presents nothing of the 
essentially impossible. This heat Tripler hopes to 
utilize. If it is utilized, there will be a further de- 
mand made upon the heat of the terrestrial system, 
which will involve a reduction of temperature due 
to the conversion of low grade heat energy into 
mechanical energy. This involves a_ theoretical 
loss of temperature by the earth and its atmosphere 
from self-contained causes, and the loss would have: 
to be replaced by heat derived from the sun. 

Perhaps the most striking feature about the Tripler 
process, apparatus and plant is that there is compara- 
tively little to be said about it. While Dewar, work- 
ing on the lines laid down years before by Pictet and 
assisted by liberal gifts from one of the London 
guilds and from private individuals, liquefied gases 
at vast expense, here in the metropolis of this coun- 
try a private individual has erected a plant at his 
own expense, and for years past has liquefied air on a 
scale which Dewar and his associates never dreamed 
of. In order to preserve air, Dewar devised his cel- 
ebrated vacuum bulb, an apparatus of the highest 
merit. Tripler took common tin cans, lined them 
with felt, filled them with two to five or more gallons 
of liquid air, and sent them off hundreds of miles by 
rail. 

In the reports of papers and discussions in English 
scientific gatherings incredulity is still expressed, or 
was until very recently, when the sending of liquid 
air about in common tin buckets was spoken of. 

In England, Dewar has excited the greatest enthu- 
siasm by his lectures on liquid air and liquefied gases. 


290 LIQUID AIR AND THE 


The enthusiasm was deserved, and it is a hopeful 
sign of the times that a popular audience can still be 
so stirred to a high pitch of interest in a scientific 
subject. But, meanwhile, Charles E. Tripler, in his 
private laboratory, with boiler, air compressor and 
simple liquefying apparatus, has repeatedly shown 
liquid air, in quantities that 
until recently scientists 
would scarcely have be- 
lieved possible of produc- 
tion, has poured it out on 
the floor by gallons to show 
its rapid evaporation and 
production of dense clouds 
of condensed moisture, has 
blown iron pipes to pieces 
with it,and has permitted 
physicians to try its effects 
as a cautery upon patients. 
Mr. Tripler’s apparatus is 
of the type which employs 
no extraneous sources of 
cold. All the liquefaction 
is done by its own powers 
and within its own system. 
Pon ne toe ton A steam boiler is installed 
the Floor in Tripler’s 1 One corner of the labora- 
Laboratory. tory in which his plant has 
been erected. This supplies © 
steam to a Norwalk straight line compressor. The 
steam pressure is about 85 pounds to the square 
inch. | 
The compressor is a steam engine with three com- 


291 


LIQUEFACTION OF GASES. 


o~ ae fb 


‘Tripler’s Laboratory, Showing Air Compressor and End of Liquefier, 


292 LIQUID AIR AND THE 


pression cylinders in line of the prolongation of the 
axis of the cylinder. The piston rods run in one 
line through the four cylinders. The engine is rated 
at 90 horse power when working at 150 revolutions. 
For the work done in Mr. Tripler’s laboratory the 
rate is about 100 revolutions. 

The stroke of the engine, and, consequently, that 
of the four compression pistons, is 16 inches. The 
steam cylinder is of 15 inches diameter, the first or 
low pressure air cylinder is of 103 inches diameter, 
the intermediate cylinder is of 6% inches diameter, 
the high pressure, the last of the three, is of 23 inches 
diameter. The pressure is brought up by three 
steps. The first compression raises it to a pressure 
ranging from 55 to 65 pounds above the atmospheric 
pressure; the next compression, from 350 to 400 
pounds; and the final from 2,000 to 2,500 pounds per 
square inch. Theareasof the pistons in the three air 
compressing cylinders are in the ratio of 110: 44: 6, 
the air pressures successively produced as 55 : 350: 
2,500. 

The cut gives a diagrammatic representation of 
the general arrangement of the apparatus in Tripler’s 
laboratory, and the cut on page 291 gives a view of 
the interior. On the left is seen the:boiler, and in 
the background is the compressor. The three air 
cylinders of the compressor are arranged in tandem 
or in line with each other. Between the first and 
second and between the second and third air cylin- 
ders are surface condensers which cool the air. 
Compression, as has been explained, heats a gas. 

The air is drawn down from the roof of the build- 
ing through a pipe, and goes through a washer 


LIQUEFACTION OF GASES. 293 


4aslog 


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pete 
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vQ 
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E 
© veoeteea py 
fa ti Steam Exhaust 
> § 
4 . To Froof 
© tn ! ; 
a S Ih Air Intake 
g pea er 
=) a OS 
Cg | QS &, 2 
x 
i 
= 
ae | 
Sera. 
2 § 
‘oe D 
wo & 
> 
vy ‘4 
a : 
S 3 
5 ve 
ag (t Ia 
oe I 
ary U———S (_ i) 
Liquetier_No./ 1 
ae ae Seestoen 
— 
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B “pe aren oe ae 
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Liquefier No.2. 


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which removes the dust. This is a case containing 
baffle plates over which water is kept trickling. It 
is marked “duster” in the diagrammatic cut. The 


294 LIQUID ATR VAND? THE 


air then goes through the compressor with its cool- 
ers and leaves the third cylinder at high pressure 
and hot. 

The heat is removed by a final cooling in a surface 
condenser designated ‘ cooling tank” in the diagram. 

The moisture in the cooled air is pretty thorough- 
ly precipitated by the compression. There are some 
traces of oil present, derived from the lubricating 
oil of the pump. Such of this material as is carried 
forward is removed in a separator, which is virtually 
a steam-trap, and the air is ready for liquefaction. 

The construction of the liquefiers has not been 
fully divulged. The lower end of one is seen in the 
cut on page 291. They appear as long felt-covered 
cylinders. Inside the felt wrappings are cylindrical 
cases containing coils of copper pipe. At the bot- 
tom of the coil of pipe is a special valve, the inven- 
tion of Mr. Tripler. The compressed air escapes 
from the valve and, expanding suddenly, experiences 
a drop in temperature. Some of the cooled air 
works its way up through the chamber and cools the 
coils of pipe. Thus there is established an intensive 
or accumulating action. The air entering the lique- 
fier at a normal temperature is cooled by the reverse 
flow of expanded air. It escapes from the valve at 
the bottom at a temperature which constantly grows 
lower until air begins to liquefy, and collects in the 
bottom of the liquefying chamber. Now all is in 
working order, air is liquetying and collecting, and 
in a short time liquid air can be drawn a by the 
gallon just like water. 

Three or four gallons of liquid air are produced 
in an hour in the usual operation of the plant, but 


LIQUEFACTION OF GASES. 295 


power enough is present to produce far more. 
Every part of the liquefiers is insulated with non-con- 
ducting covering. Only the handles of the valves 
protrude, and these become white with a thick de- 
posit of hoar frost. 

The diagrammatic cut gives a general idea of the 
distribution of parts, but is not given as a representa- 
tion of the plant in any sense. 

One of the most remarkable things about Mr. 
Tripler’s work is its simplicity even in detail. 
There is no refrigerant used, and nothing is to be 
seen but the ordinary objects which meet the eye in 
any steam plant. There are no cylinders of liquefied 
ethylene or carbon dioxide. Even the compressor 
is of anormal type. Yet in this apartment the most 
‘impressive achievement in physics of the century is 
repeated week after week, and air is liquefied by 
the bucketful and handled as if it were so much 
water. 

Its transportation is interesting. No vacuum bulbs 
are needed for this. A tin bucket is wrapped with 
boiler felt and is thrust into a:larger one. The liquid 
air is poured into the inner bucket, a piece of felt is 
placed over the mouth, and the air is ready for re- 
moval. In such buckets it has been taken hundreds 
of miles. 

In the cut on the next page are given sections of 
two of the buckets, one holding twice as much as the 
other. The scale is 14 inches to the foot. 

Mr. Tripler has given many lectures on the subject 
of liquid air, and in the next chapter are illustrated 
a number of the experiments which he shows. But 
his goal is the practical, and his lectures are merely 


296 LIQUID AIR AND THE 


a side issue and express only his deep interest in the 
subject. 

An interesting occasion was the presence of Prof. 
Raoul Pictet at one of Mr. Tripler’s demonstrations. 
The American inventor tells of Pictet’s enthusiasm 
at witnessing the demonstrations executed with such 


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Tripler’s Buckets for Transporting Liquid Air. 


prodigality of material. The originator of the cas- 
cade or closed cycle system of liquefaction met the 
originator of the self-intensive system only to be 
delighted at his demonstrations. | 


LIQUEFACTION OF GASES. 297 


GHAPTERS XI. 
THE JOULE-THOMSON EFFECT. 


First attempts at liquefying gas—Joule and Thomson and 
their discovery—-Coal a cheap chemical—Substitution of 
mechanical for chemical energy—Sir William Siemens’ 
regeneration of cold—Self-intensive refrigeration—Nega- 
tive Joule-Thomson effect—Mathematics of the theory— 
Conditions of pressure for economical application. 


The first attempts at liquefying gases were based 
on the application of great pressure. This was at 
once useless and unnecessary in. many cases; useless 
because an insufficient lowering of temperature was 
applied and the gases did not liquefy, and unneces- 
sary because the high pressure was not needed, had 
a sufficient refrigeration been applied. Cailletet, 
and probably Pictet, got useful effects indirectly 
from high pressures. By sudden release of: high 
pressure a great refrigeration was produced, the 
temperature of the gas fell below the critical point 
and it liquefied. 

The discoveries due to Joule and Thomson that air 
and most gases are not perfect gases, that there is 
really no perfect gas, and that hydrogen is an ultra- 
perfect gas, has already been spoken of on pages 60 
et seg. The change of temperature in a given mass 
or volume of gas brought about by letting it flow 
under pressure through an orifice, an effect not to be 
confused with cooling due to expansion, while so 


298 LIQUID AIR AND THE 


trifling as to have entirely escaped recognition by 
Joule in his early experiments, has been taken as the 
starting point for the operation of refrigerating ma- 
chines. The movement, whether we accept the 
theory of action offered or not, was in the direction 
of purely mechanical production of cold, and hence 
was in the direction of economy. Dewar speaks 
often of the great expense of his liquefactions, in 
effecting which a very large expenditure was in- 
‘curred in the production of liquid ethylene alone, so 
that the cost of this and of other refrigerants was 
a large item of expense in the Royal Institution 
work. 

In general terms we may say that coal is the: 
cheapest chemical we possess. Could the old 
time experimenters have seen the possibility of sub- 
stituting coal for the expensive liquefied ethylene 
and other gases, they would have been most de- 
lighted. In the processes of liquefying air and oxy- 
gen which we are now to describe this in a sense is 
done. Air is liquefied by the application of power, 
and neither liquid ethylene, solid carbon dioxide nor 
other refrigerant is needed. Even coal may be 
dispensed with, for the energy of a waterfall might 
be utilized to produce liquid air. 

As a general rule, it may be stated that the sub- 
stitution of mechanical power for chemical and for 
other special agents is one of the most impressive 
movements of the age. The electric battery giving 
way to the mechanically impelled dynamo is an ex- 
cellent example of the movement alluded to. In the 
field of refrigeration the substitution of a purely me- 
chanical process for refrigeration by boiling liquefied 


LIQUEFACTION OF GASES. 299 


gases was to be greatly desired, and in the applica- 
tion of the Joule-Thomson effect the possibility has 
been claimed of effecting the substitution. 

When gas expands under terrestrial conditions, it 
practically always falls in temperature. It is not 
easy to see how conditions could be established which 
would expand a gas without such fall. This fact was 
well known for many years, and over forty years 
ago the idea of applying it to refrigeration and of 
making it more effective by cold regeneration was 
suggested. It was William Siemens who saw the 
possibility of utilizing it by a regenerative process 
for the production of still lower temperatures. It is 
fair to presume that his mind was, at the period in 
question (1857), deeply occupied with the subject of 
the regeneration of heat, and the regeneration of 
cold seemed a natural sequence of the other. He 
simply thought of the cold due to the energy de- 
veloped by an expanding gas. This development of 
energy calls upon an equivalent quantity of energy 
for its development, and in the caseof an expanding 
gas the energy which is called upon is the heat 
energy of.its molecules. This heat energy is con- 
verted into mechanically exerted energy and dis- 
appears as heat—therefore cold is produced. . 


Leaving out of account this refrigeration, we know | 


that, if a gas is expanded, there is another change in 
temperature outside of and independent of the 
natural cooling due to energy developed in expan- 


sion. This is what we have termed the Joule-Thom. 


son effect. The apparently slight refrigeration thus 
produced is the principle claimed to underlie the 
operation of two of the most prominent of the gas 


eee nemo 


ve nareneanene: 


ety 
300 LIQUID AIR AND THE, 


liquefaction processes now in use.  Linde’s and 
Hampson’s apparatus are the ones alluded to. 

There is nothing of efficiency involved in the 
small orifices or porous diaphragm as used in the 
experiment. It is simply a way of localizing expan- 
sion and of producing it. As it is an element of the 
most practicable way of rendering possible the ex- 
pansion of a gas from a high degree of compression, 
it is always used, but there is nothing occult about it 
as far as the valve or aperture is concerned, outside 
of mechanical advantages. 

The term self-intensive refrigeration is perhaps 
etymologically preferable to regeneration. This pre- 
ference would be based on the idea that the produc- 
tion of cold is not, properly speaking, an operation 
involving production, but destruction. Cold is the 
negation of heat, and, properly speaking, cannot be 
said to have an existence of its own. But William 
Siemens, doubtless thinking over his methods of re- 
generating heat, in his 1857 patent prescribes the 
regeneration of cold. 

The origin of the methods used by Tripler, 
Hampson and Linde can be studied in the records of 
the patent offices as well as in the literature of pure 
SE1lence. 

The primary idea of the self-intensive process is 
found in the Siemens provisional specification of the 
English Patent Office. He simply contemplates 
cooling air by expansion, thereby causing its heat 
energy to disappear. This cooler air is caused to 
act upon the entering air, and give it a lower tem- 
perature before expansion, so that the cold grows 
constantly more intense. But Siemens has no idea 


LIQUEFACTION OF GASES. 301 


of utilizing the expansion through a small orifice, 
which is the system so much employed at present. 
The Joule-Thomson effect was not known at the 
early date which we speak of. 

In 1893 Tripler applied for and was granted a 
patent by the English Patent Office for a gas lique- 
fying process and apparatus. This most interesting 
document gives a clear description with drawings of 
an apparatus based on self-intensification for the pro- 
duction of cold. The Joule-Thomson effect is not 
appealed to in it. 

It is farfrom certain that the Joule-Thomson effect 
is the principal factor in the operation of modern 
self-intensive gas-liquefying machines, even if we ad- 
mit Onnes’ theory that the negative effect which 
obtains with hydrogen is reversed under more ex- 
treme conditions. We are justified in attributing 
especial importance to such utterances as those con- 
tained in Siemens’ early provisional specification, 
and in Tripler’s early patent, which is full and com- 
plete and is illustrated by drawings. 

The use of an aperture for expanding gas through 
is more justly regarded as an expedient for readily 
bringing about a great difference in pressure in a gas 
or, what is the same thing, for causing agreat expan- 
sion and sharply locating it. 

But whatever influence the Joule-Thomson effect 
has, whether great or small, Linde and Hampson 
have both invoked it as the principle on which their 
machines operate. It is easily stated, and involves 
in its study but little mathematics. In Cailletet’s 
and in Wroblewski and Olszewski’s liquefactions by 
release there was no thought of appealing to this 


302 LIQUID AIR AND THE 


almost trifling effect to account for the mists of 
oxygen and other gases observed when they sud- 
denly expanded. The cloud of moisture seen in the 
receiver of a common air pump with the first strokes 
of the pump were never supposed to be due to it. 
It is not clear why it has to.be invoked as the factor 
in liquefying air by the gallon. 

The theory may be thus stated : 

If air be expanded through a fine orifice, the 
change in temperature due to the Joule-Thomson 
effect is thus calculated : 


Fall in temperature — 


Val — p} a 
an 


In this formula 7’ is the pressure in atmospheres 
before passage through the orifice or before expan- 
sion, f' is the pressure after passing through it or 
after expansion, 7! is the temperature of the gas 
before passing through it in degrees Centigrade re- 
ferred to the absolute zero. 

The work which a pump has to do in forcing a 
continuous circuit of air round and round through 

2 


this aperture varies with — This is because the 
yo 

work of the pump depends on the ratio of pres- 
sures on the front and back of the piston. The 
greater the pressure in front in proportion to the 
pressure back of it, the more work it has to do. 

To get a good reduction of temperature, it is evi- 
dent that the quantity 7’ — p' of the first formula 
must be as large as possible and the quantity 7‘ of 


LIQUEFACTION OF GASES. 303 


the same formula must be as small as possible. The 
first of these is regulated by the proportions given 
the different parts of the apparatus, the second quan- 
tity grows smaller as the temperature of the gas to be 
liquefied falls. In circulating apparatus, this tem- 
perature, as we shall see, falls continuously, the longer 
the apparatus is worked, until air begins to liquefy. 
2 
The ratio— may be kept small and the difference 
P 
f—' large by giving high values to f” and f'; in 
other words, by working at high pressures. 

A formula often seems uninteresting, but if the 
substitutions of real values for the letters are made, 
it acquires concrete interest. 

Assume that the air, in passing through the orifice, 
falls 3°6 atmospheres in pressure, and assume that 
we start with a temperature 7‘—o0° C.—273° C, ab- 
solute. The fact that the fall in pressure is 3°6 
atmospheres makes /’—/'—3°6. Our formula now 
reads: 

Fall-of temperature 23 (243)—1° C. (18° FE.) 

This seems a very trifling fall of temperature. 

But assume that the air is driven more vigorously 
through the orifice until a difference of pressure of 
ten atmospheres is maintained, then the formula 
reads: 

Fall of temperature — 12 (883)—2:78° C. (5° F.) 
which is at least somewhat more appreciable. So it 
follows that by changing the mechanical relations 
we can produce falls of temperature of various de- 
grees. 

On inspection of the formula another thing be- 


204 LIQUID AIR AND THE 


v 


comes evident. The lower the temperature before 

passing the orifice is, the greater will be the fall in 

temperature. To assume 7! to be —g1° C. (—131°8° 

F.), which is in absolute degrees C. 273—g1—182° 
289\? 

C., the quantity —) reduces to the factor 2°52 in 


round numbers; so that if the gas, as it reaches the 
diaphragm, can be got down to this temperature, the 
fall in temperature will be greater in the ratio of 
(Bee)? s (239) 112 (252,00 tc2:25, -alsosine note 
numbers. Hence, at this temperature, for the two 
pressure differences we have taken, the tempera- 
tures would :be! 1°-X 2°25 —= 2°25" GC.) ( (Oh ie eae 
278° 225 = b'20° Cems ean 

The first substituted formula has been purposely 
constructed so as to give a temperature fall in round 
numbers of 1° C. If there is a different pressure 
drop employed, the fall of temperature due thereto 
when, 71—= 273°C. absolute.or:0° .C. 1s ioundwby 
dividing the pressure drop expressed in atmospheres 
by 3°6 and multiplying by unity. This gives directly 
the fall in temperature. 

Thus, if a fall of 10 atmospheres were to be as- 
sumed, we have 10+ 3°6— 2°78, which, multiplied 
by unity, gives 2°78° C., as calculated by the second 
substituted formula. 

Assume now that we are working with a different 
temperature, 7’. Then we may divide it by 273 
and square the product and divide unity with it, and 
the result will give the degrees Centigrade of fall of 
temperature at a pressure drop of 3:6 atmospheres. 
Thus suppose- the temperature 71 to be —g1° C. 


LIQUEFACTION OF GASES. 305 


This is 182° C. absolute. 4$2—%, which squared is 
§. To divide unity with it, we invert and multiply, 
which is expressed thus: }x 1— 2:25. This is the 
factor used in the third substitution example. 

It is evident that with a formula for a fall of 
temperature — 38 (343)? — 1°, we can, by applying 
thereto the two methods of calculation last described, 
make it apply to any case. Thus, if we assume that 
the pressure drop is 10 atmospheres and that 71— 
—g91° C., we have simply to multiply unity by one of 
the factors already determined, and this product 
must be multiplied by the other. These factors are 
2°78 and 2°25; we have, therefore: 

Deyo 6 22h Ons. Ce( 11:27 eis) 

The same result could be reached by substitut- 

ing directly in the equation 


Fall of temperature = 


p—P' (=) 


4 273 
These examples merely illustrate different ways of 
reaching the same results. 
The statement has been made that the power re- 
quired to force air through the aperture varies with 


9 


es in which 7’ is the pressure in the inlet side of the 
P 

aperture and #' the pressure of the gas after it has 
passed through it. The reason of this propor-. 
tion existing is due to the fact that gas is diminished 
in volume by pressure. Thus, if a given weight of 
air is to be pumped through an aperture by a pump, 
it may be done at very low pressure or at high pres- 
sure. At first sight it might be thought that at high 


306 LIQUID AIR AND THE 


pressure, when the pump is working against a pres- 
sure of fifty pounds to the square inch, more power 
would be required than when it works against a 
lower pressure. But, air being compressible, the 
pump at high pressure has a less volume of air to 
force through, and hence has fewer strokes to make. 

The air which enters the suction end of the pump 
may be looked upon as reinforcing its action. 
Hence the higher its pressure is, the less work will 
the pumps have todo. Hence the smaller 7’ is and 
the larger ' is, the less work will the pump have 
to do. 7 


LIQUEFACTION .OF GASES. 307 


GHAPRTER == XLV; 
THE LINDE APPARATUS. 


Linde’s apparatus— The simplest form of apparatus—lIts 
‘ operation—Its storing of air at atmospheric pressure— 
_ Avoidance of atomization and waste—Subdivision of 
pressure-drop—Laboratory apparatus—A feature of ineffi- 
ciency in it—Its power of liquefaction—Continuous oxy- 
gen-producing apparatus—Date of Linde’s first successful 

use of his apparatus. 


Linde’s apparatus, which is described as utilizing 
this small increment of cold, if the expression may be 
allowed, and by constant summation of such incre- 
ments bringing about a high degree of refrigeration, 
caused much interest when its supposed principles 
were first stated and its operations were first dis- 
closed. The term self-intensive has been aptly coined 
to describe machines of this type. 

W hat the apparatus of the original Linde type does 
is this: Airis pumped through a circuit of pipes; 
the pipe from the outlet of the pump, after going 
through the given circuit, returns to the inlet, so 
that the air under treatment goes constantly around 
the same circuit. When a gas is pumped against 
resistance, it is compressed or diminished in volume 
and heated. The outlet pipe from the pump is kept 
at a uniform temperature by cold water circulating 
in contact with the outside of the pipe, like a surface 
condenser. 


308 LIQUID AIR AND THE 


The air thus cooled is forced through a small aper- 
ture, and the passage from high to low pressure, with 
consequent expansion, causes cooling. Between the 
water cooling apparatus and the aperture a long 
length of pipe intervenes. The cooled air is carried 
back to the pump so as to circulate around this pipe 
on its way back, and it abstracts heat from the air 
already cooled by the water. Hence the air reaches 
the aperture constantly at a lower temperature, 
but leaves the water condenser always at a uniform 
temperature. The real cold production is done 
after the air leaves the water condenser. The degree 
of cold keeps increasing until liquid air drops from 
the aperture and lies in the bottom of the apparatus. 
By a cock it can be drawn therefrom like water. 

It seems at first sight impossible that the small de- 
crease of temperature, due to the imperfection of the 
gaseous State as it exists in air, should be able to pro- 
duce such refrigeration. What Hampson calls ther- 
mal advantages are to be aimed at. The surface on 
which the cooled air acts on its return must be 
large, the material of the pipes thin. These elements 
provide for a rapid cooling by the returning air 
of the counter-stream on its way to the aperture. 
The entire mass to be cooled must be as light as pos- 
sible. The action of the pump is constantly heating 
the gas by compression, and this heat 1s removed by 
the water. The atmosphere surrounding the appara- 
tus constantly heats the portions colder than itself 
by contact. The colder portions, therefore, must be 
protected from this action by thick jacketing or other 
means. Concentric air spaces produce a good effect, 
and doubtless if it were practicable Dewar’s vacuum 


LIQUEFACTION OF GASES. 309 


heat insulation might be applied with excellent 
effect. 

Linde made quite a sensation by his description 
of his apparatus, which, by purely mechanical means, 
liquefied air, although his first results were far from 
encouraging. 

W hat is called Pade s simplest form of apparatus 
is illustrated in the cut, and will be readily under- 
stood, especially if the reader has grasped the very 
simple general theory on which its operation depends. 
It will be understood that the drawing is not a repro- 
duction of the exact apparatus, but is diagrammatic, 
being purposely made as clear as possible without 
permitting detail to interfere with intelligibility. 

P represents a pump which aspirates air from the 
pipe, G, and forces it out, under pressure, through /7, 
The air forced out through ff goes through a 
complete circuit of pipes and returns arent G, 
thus constantly and repeatedly going around the 
circuit. | 

J is a water condenser or more properly a cooling 
apparatus. It is a cylindrical vessel, and the air pipe 
goes through it in a coil. Water enters at K and 
emerges at Z, so that as the gas leaves the vessel it is 
always at the temperature of the inflowing water. 
The arrows show the direction of the current of gas, 
and allis perfectly clear to the point, C. The arrows 
might be taken to indicate that the gas, on reaching 
C, goes down directly to G, but they do not indicate 
this. The pipe, J, is of small diameter, and, without 
any opening or break, runs straight on to D, is bent 
into a coil, and descends to £ and 7. But from Cto . 
F it is surrounded by a second pipe concentric with 


310 LIQUID AIR AND THE 


it, and it is this outer pipe which is connected to 
the pump suction by the vertical pipe extending 
downward from C and ending in G. 

The cylindrical vessel on the right is simply a non- 
conducting casing or jacket to protect the pipes from 
the heating effect of the outer air. In the illustration 


Linde’s Apparatus for Liquefying Air. 


the interior of the coil is shown, a part of the pipe 
being supposed to be broken away to show this. 

In the course of the air in the pipes to the right of 
the point, C, lies the soul of the apparatus. The 
small pipe running down through the protecting 
vessel terminates in the chamber, 7. <A valve, R&, is 
provided which may be opened or shut so as to reg- 
ulate the pressure drop, and this valve constitutes 


LIQUEFACTION OF GASES. 3II 


the aperture through which the gas passes and ex- 
pands with attendant cooling. 

The end of the pipe, 4, enters the small airtight 
box, orm Chamber, 7. Prom the chamber rises“a 
larger pipe, /, which, just above the top of the 
chamber, receives within it the smaller inlet pipe, Z, 
and winds up through the protecting vessel concen- 
tric with the smaller pipe. On the second and third 
turns from the top the interior arrangement of the 
pipes is shown very clearly. 

The operation is now clear. The air enters the 
pump at G, is forced through AH and compressed, 
thereby being heated. The heat is removed in the 
cooling apparatus, /, and the compressed air, at the 
temperature of the water, goes on to D. There it 
descends in the inner pipe of the double coil, expands 
through & and is cooled thereby, passes through 7 
and up through F, the outer pipe of the coil. There 
it cools the air in the inner pipe of the double coil. 
The air, therefore, reaches the valve, R, at a lower 
temperature than before, so that it is constantly fall- 
ing in temperature, reaches R at lower and lower 
temperatures, and eventually the critical temperature 
of liquid air is reached and passed, and liquid air 
begins to collect inthe chamber, /, as shown in the 
cut. By the faucet, V, it can be drawn therefrom as 
‘required. 

If air is liquefied in the apparatus, every cubic inch 
of liquid represents about one-half a cubic foot of air 
withdrawn from circulation in the apparatus. Once 
the apparatus begins to liquefy air, it has to have new 
material supplied it, just as a grist mill needs a sup- 
ply of grain to keep the stones in operation. A pipe 


312 LIQUID "AIR AND THE 


at A connects with a second pump which pumps in 
new air as required, so as to maintain an advan- 
tageous pressure in the system—one which will give 
an economical relation between the pressures on the 
opposite sides of the aperture. 

A minor yet important feature of this apparatus 
is that the liquid air collects at atmospheric tempe- 
rature, or thereabout. The effect is twofold. It 
can be withdrawn much more easily than when it 
has to.be taken from a receiver in which itis sub- 
jected to 50 or 100 atmospheres pressure. «In the 
latter case it rushes out, only controllable by the 
faucet, and the mechanically atomizing effect plays a 
part in wasting it and facilitating its loss by gasifica- 
tion. But, stored under atmospheric pressure, it not 
only is quietly withdrawn, as required, but, by vola- 
tilization, it keeps its own temperature down. The 
maintaining it in a quiet state and in bulk operates 
to make it evaporate more slowly, the battle of the 
squares and the cubes, as it has aptly been termed, 
being involved. 

It is evident that to make the difference of pres- 
sure ~?—/! (page 302) large, recourse may be had to 
the expedient adopted in steam engineering for ex- 
pansion engines of high initial pressure. These are 
constructed with two cylinders (compound engines) 
or with three or more cylinders working in series, 
the steam passing seriatim from one cylinder into 
the next (triple, quadruple, etc., expansion engines). 
_ Just as in these engines the expansion is divided be- 
tween several cylinders, so it is practicable in self- 
intensive refrigerating machines to force the air or 
gas through several apertures, letting each one take 


LIQUEFACTION OF GASES. cats 


care of its fraction of the total difference of pres- 
sures, p*—p'. 

Linde has done this in a partial way in his labora- 
tory apparatus, and the cut shows the modification 


ia) 


Laboratory Apparatus. 


in question. If the description of the simple appa- 
ratus has been understood, the drawing alone will be 
almost self-explanatory. There are, however, vari- 
ous refinements introduced in this machine which 
need explanation. 


314 LIQUID AIR AND THE 


A double-barreled pump is used which takes in 
air from the open room, the pipe on the right, with 
the arrow pointing down it, being the intake. The 
right hand pump cylinder pumps the air through 
the coil in the water jacket, ce, and thence it passes 
into the cylinder on the other end of the pump. On 
its way to the other or left hand end of the double 
pump, it is joined by a stream of air from the inter- 
changer or refrigerator, which air enters by the pipe, 
f:, From the left hand pump barrel the air, now 
twice compressed, goes through a- second water 
jacket, d, and by the pipe, P*, passes to'the left. 
These water jackets cool the air but partially. In 
order to more thoroughly cool it water is injected, 
and at f is a trap which removes most of the water. © 
The air then goes through a coil in the small tank, 
g, which is surrounded by ice and salt. This cools 
the air thoroughly and removes the last of the water. 

It will be remembered that in the first described 
apparatus an auxiliary pump was used to supply 
the deficiency of air, due to liquefaction of a portion 
thereof. In the laboratory apparatus the right hand 
pump barrel performs this function, compressing 
the air to 16 atmospheres only; the second or left 
hand pump barrel, taking in the air from the right 
hand barrel, and also the air from the pipe, P!, com- 
presses it all to 200 atmospheres. 

The air thus compressed we have followed to its 
exit from the coilin g. Cold and dry, it rises to the 
top of the refrigerating case, entering it at P*? and 
going down a spiral pipe. This spiral pipe is the 
inner one of atriple concentric coil, whose construc- 
tion is shown in the small sectional cut in the upper 


LIQUEFACTION OF GASES. 315 


right hand corner of the illustration. It descends 
through the interior coil to a, where it passes 
through an aperture regulated by a valve. Just be- 
low a is another valve, 6. This valve is slightly 
opened, so that, of the air which passes a, one-fifth 
as near as may be passes 4. The four-fifths of the 
air which does not pass through @ rises through the 
annular space between the interior tube and the in- 
termediate tube. This four-fifths of the air rises to 
the top of the refrigerating chamber and goes back 
to the pump by the pipe, P! P'. This circuit is com- 
parable to that in the first described machine. 

The one-fifth of the air which passes through 4 
has undergone a double expansion. It has expanded 
through two apertures, @ and J. A portion of it 
when the liquefaction has begun passes on to the 
annular space between the intermediate pipe and the 
outside pipe of the coil, and, after passing through it, 
escapes into the open air at the top of the chamber. 
The outlet pipe is there shown leading from the out- 
side tube up into the air. Three-quarters of it thus 
escape, one-quarter is liquefied and collects in the 
double-walled vessel, c. Thus, the air from the 
pump, entering the inner pipe at P”, is cooled on its 
descent by the expanded air in the intermediate 
pipe. But this air is stili further cooled by the con. 
stant uprising stream of still colder air rising in the 
outer pipe. 

There is one peculiarity to be noted in the accu- 
mulative cooling action. The air from the pump 
entering at /” is working in the opposite direction 
to the colder air in the intermediate annular space 
or pipe. This is the correct method. But the cool- 


316 LIQUID AIR AND THE 


ing effect of the air in the outer tube is differently 
applied. This air rises, and cools in its rising the 
air in the intermediate tube, which is also rising. 
This is the wrong way of working, but its inefficiency 
is lessened by the fact that the entire quantity of air 
does not pass through the outer tube. Itis only a 
question of one-fifth multiplied by three-quarters, 
which is three-twentieths of the original air. This 
is the quantity which passes up the outer tube. It 
operates, perhaps, more as a jacket than as a cooler. 

The air, after it collects in the liquid state in the 
vessel, c, can be withdrawn by opening the cock, #. 
Enough back pressure is maintained in the vessel, c, 
to force the liquid air out at 4, exactly like water 
from a soda water siphon. 

It will be seen that the right hand pump barrel has 
to supply not only the deficiency in air caused by 
liquefaction of a portion of it, but has also to pump 
in air to supply the loss of that which escapes into 
the air after passing through the valve, 0. 

Another peculiar feature will be noticed. All of 
the air is not twice expanded. The majority is only 
once expanded, and all the liquid air which is pro- 
duced is derived from the one-fifth of the total which 
is twice expanded through a and through 4. 

A pressure gauge is mounted on top of the trap, 
f,to enable the operator to maintain the proper 
pressure. 

This apparatus, with the expenditure of three 
horse power, is credited with the production of 
nearly one quart of liquid air per hour. 

The makers of liquid air, confronted with their 
great success, as yet scarcely know what to do with 


LIQUEFACTION OF GASES. 


their wonderful product. 


317 


One of their projects is 


to utilize it for the production of a highly oxygen- 
ated air, as it may be termed, for the production 


of a mixture of nitrogen 
and oxygen which will 
be very rich in oxygen. 
The next illustration 
shows in diagram how 
Linde proposes to effect 
this by a continuous pro- 
GCesseeethe they.cut sare 
shown a double set of 
annular or concentric 
pipes, forming two coils 
such as used in the first 
described apparatus. 
These coils are in paral- 
lel with each other. The 
air from the pump enters 
both coils by the small 
branched tube seen at the 
top of the apparatus and 
designated by a. It goes 
down the two _ interior 
tubes of the coils through 
the valves, c and d, and, 
leaving the outer con- 
- centric pipes, the tubes 
unite toa single pipe, &. 
Thence the single tube 


, i 
aS SS SS SS eS 


Linde’s Oxygen-producing 
Apparatus. 


passes through the liquid air vessel, S, and emerges 
atthe bottom. The air expands through the valve, 
r', and part of it liquefies and collects in S. 


318 LIQUID AIR AND THE 


When air is liquefied and allowed to stand, it gives 
off nitrogen much more rapidly and in larger quan- 
tities than it does oxygen. Hence, a gas rich in 
nitrogen is given off by the liquid air in S, and this 
gas rises through the annular space between inner 
and outer pipe in the coil, which starts from the left 
of the liquid air vessel. 

The liquid air, constantly growing richer in oxy- 
gen, passes out of a pipe leading to the right out of 
the bottom of the liquid air vessel and, controlled by 
the valve, 7’, evaporates into the annular space of 
the other coil. The nitrogenous gas in the one 
annular space and the gas rich in oxygen in the 
other annular space cool off the gas from the pump 
so as to form the true self-intensive heat interchang- 
ing system. : 

The two outer pipes are kept separate as they 
emerge from the interchanger. One, marked x, de- 
livers a product poor in oxygen. This may be allowed 
to escape. The other, marked 2a, delivers a product 
rich in oxygen, which may be utilized for many 
technical purposes. 

If the gases from the outer pipes of both coils are 
allowed to escape, one into the air, the other into an 
oxygen receiver, the pump will have to work upon 
new air constantly. There will no longer be a ques- 
tion of supplying a loss of a fraction of the air—all 
will have to be pumped in during the operation. 

Linde’s first successful experiments were per- 
formed in May, 1895. Fifteen hours’ pumping was 
required to liquefy air, and then he collected some 
three quarts of liquid air per hour, containing about 
70 per cent. of oxygen. He used in his interchanger 


LIQUEFACTION OF GASES. 319 


iron tubes over 300 feet long, 1°2 and 2°4 inches 
in internal diameter respectively. His pump was a 
carbon dioxide or carbonic acid gas compressor, 
and he got from it a compression varying from 22 
to 65 atmospheres. The liquid was crystal clear and 
bluish in color. 

_ The inventor’s own words describe his apparatus 
as eliminating heat from gas “exclusively by ex- 
penditure of internal work.” This internal work he 
holds to be the work of separating the gas’s own 
sluggish molecules from each others’ vicinity. 


320 LIQUID AIR AND THE 


GHARTIER eXVe 
THE HAMPSON APPARATUS. 


Hampson’s apparatus—Its general features of construction— 
The jet and regulating device—Thermal and mechanical 
advantages—Data of its operation—Use of cylinders of 
compressed gas instead of pumps—Application of pre- 
liminary cooling to the air or gas to be liquefied. 


The Hampson apparatus is the invention of Dr. 
W. Hampson. It is very simple and resembles very 
much the Linde apparatus, and it works precisely on 
the same lines. 

The cut shows a section of the apparatus. A 
cylindrical case is lined with non-conducting mate- 
rial. It contains three coils of pipes, each coil con- 
sisting of a single range of pipes arranged almost in 
the shape of a cylinder. The coils of pipe are laid 
in what may be termed the grooves of helices or 
screws, formed by winding partitions whose course 
is parallel with the axes of the coils of pipe, so that 
the section of the apparatus shows the circular tube 
sections, each in a little square. The perspective 
view of the end of the innermost coil on page 322 
shows how the pipes and partitions are disposed. 

The air enters by the small tube at the upper right 
hand portion of the case. It goes down the long 
outer helix, passes to the bottom of the intermediate 
one, and rises through its coils to the top. Here it 


LIQUEFACTION OF GASES. 321 


passes into the central coil and descends to the bot- 
tom of it, near the lower end of the liquid air 
reservoir. The air here issues | 
through a jet into the body of 
the apparatus. It follows the 
course of the helically bent 
pipes; first up the center, then 
down the intermediate cham- 
ber, and then up the exterior 
chamber, escaping at the larg- 
er pipe. Its course, it will-be 
observed, is exactly contrary 
to that followed by the air on 
its journey within the pipe. 
The helical partitions guide 
it on its return course. 

The jet through which the 
gas expands is shown in the 
next cut. Its delivery capa- 
city is regulated by screwing 
toward its face or away from 
it the flat, or nearly flat, piece 
shown. The smaller its deliv- 
ery capacity at a given pres- 
sure, the greater is the differ- 
ence of pressure or degree of 
expansion which it establishes 
at any pressure. 

In illustration on this page, 
showing the internal arrange- Hampson’s Gas Lique- 
ment of the coils, it will be CARREY ca) PENCE 
seen that the upturned jet points to the center of a 
threaded aperture, a pipe from which extends to the 


NIG 
oe a 
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ae : 


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z ca aN 

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ated 


322 LIQUID AIR AND THE 


top of the apparatus. 


Through this aperture a long 


stem passes, with a screw near its bottom and an 
almost flat end. By screwing the rod up or down, 


Jet, Regulating Apparatus, 
and Regenerative Coil 

of Hampson’s Gas Li- 

' quefaction Apparatus. 


the flat end is brought near- 
er to or withdrawn from the 
jet, as described, the deliv- 
ery of the aperture is made 
greater or less, the whole 
operating as a regulating 
valve, and, there being no 
interior parts, the chance of 
any obstruction is minim- 
izedai.s The. valve sradme 
shown in place in the cut 
showing the full apparatus. 

The pipes are made as 
thin as possible, in order to 
facilitate rapid and efficient 
cooling. The compressed 
and the expanded air are in 
finely subdivided volumes, 
so that they readily inter- 
change temperatures, and 
the long and devious course 
in opposite directions, fol- 
lowed by the two divisions 


of the air, conduces to the 


same end. 

The action has been fully 
explained already in the 
description of the Linde 


machine. The compressed air expanding becomes 
cool. The cooled gas following the coils cools the 


LIQUEFACTION OF GASES. 323 


air within them. The temperature constantly falls, 
and presently liquefaction occurs. The liquid air 
collects in the reservoir below the main case. 

The apparatus is operated by a compressor or by 
the use of cylinders of compressed air. 

The compressor must deliver air at a pressure of 
80 atmospheres or over. An engine power of 3°5 
horse power is required to drive the compressor, 
and about 1°2 quarts of liquid air are produced in 
an hour. No preliminary cooling is required. 

If the compressor delivers air at a pressure of 
120 atmospheres, air begins to liquefy in 16 minutes ; 
if at a pressure of 130 saa only 10 minutes 
are required. 

If a cylinder of compressed oxygen is used instead 
of the pump, the conditions are less favorable, as the 
pressure constantly falls. Cylinders adapted for the 
purpose can be procured. When such are employed, 
an auxiliary cylinder of liquid carbon dioxide 1s 
needed. This is used to cool the apparatus prelim- 
inary to the admission of oxygen. The latter is 
compressed to 120 atmospheres. One hundred and 
twenty-five cubic centimeters can be collected there- 
from. 

_ The preliminary cooling by the carbon dioxide is 

effected by passing the gas, intensely cold from its 
gasification, in at the bottom of the apparatus, so 
that it follows the general path followed by the 
escaping air or oxygen in the regular operation of 
the apparatus. 

It will be seen that the idea of circulating the 
identical air over and over again is not carried 
out. All that does not liquefy escapes. But this is 


324 LIQUID AIR AND THE 


merely a detail. If oxygen or any expensive gas 
were being condensed, the cheapest way would be 
to use it over and over again, and this could readily 
be done by a compressor with its inlet connected 
to the outlet of the apparatus. 

There is one important point to be considered in 
working with a compressor as contrasted with the 
use of a cylinder of compressed gas or air. The 
action of the compressor heats the gas or air; so 
it is advantageous to cool it by water, or otherwise, 
before admitting it. 

But if a cylinder of compressed gas is used, there ts 
no heating. There is evena reduction of temperature, 
due to expansion; so that an advantage is gained. 

This applies to any similar liquefaction apparatus. 

In Dr. Hampson’s laboratory apparatus the liquid 
air or oxygen can be withdrawn from its recipient 
by siphon, or the receiver can be removed with its 
contents by unscrewing a vulcanite cap at the bot- 
tom of the apparatus. 

The disposition of pipes varies somewhat in differ- 
ent types of apparatus, but the same principle is fol- 
lowed in all of them. The great object to be attained 
is lightness of the interchanging system of pipes, in 
order to increase thermal conductivity. 


LIQUEFACTION OF GASES. 325 


CHAPTER OX VE 
EXPERIMENTS WITH LIQUID AIR. 


Experiments with liquid air—Formation of frost on bulbs— 
Filtering liquid air—Dewar’s bulbs—Ljiquid air in water 
—Tin made brittle as glass—India rubber made brittle— 
Descending cloud of vapor—A tumbler made of frozen 
whisky—Alcohol icicle—Mercury frozen—Frozen mer- 
cury hammer—Liquid air asammunition—Ljiquid air as 
basis of an explosive—Burning electric light carbon in 
liquid air—Burning steel pen in liquid air—Carbon 
dioxide epee ants air liquefied—Magnet- 
ism of oxygen. 


We shall now describe some of the lecture experi- 
ments with liquid air. These are generally repro- 
ductions of experiments shown prinout lc cel 
by Charles E. Tripler at his lec- ! . 
tures and demonstrations. For 
most of the illustrations our 
thanks are due to the Sczentzfic 
American and to McClure's Maga- 
Zine. ; 

When liquid air is poured into 
a glass flask it boils energetically, 
and the outside soon becomes 
covered with hoar frost, and 
clouds of moisture condensed 
from the atmosphere descend 
from it. From its mouth the 
same cloud is seen apparently 


326 LIQUID AIR AND THE 


escaping. But this cloud has nothing to do with the 
liquid air itself. It is simply the moisture of the 
atmosphere condensed by the cold of the air as the 
latter evaporates from the liquid state. 


By courtesy of McClure’s Magazine. Copyright, 1898, by The S. & McClure Company. 


Filtering Liquid Air—Frost-coated Bulb. 


The above cut shows the filtration of liquid air 
into a Dewar bulb. Ordinary filtering paper is em- 
ployed, and the solid or cloudy matter, such as solid 
carbon dioxide, is effectually removed, and a beauti- 


LIQUEFACTION OF GASES. 327 


fully clear bluish liquid drops into 
the bulb. The bulb on the right is 
one just showing a coating of hoar 
frost. 

If a Dewar bulb is substituted 
for the flask, the air les compara- 
tively quiet. Ina good bulb only 
one or two tiny threads of bub- 
bles rise through the liquid, re- 
minding. the observer of cham- 
pagne whose. effervescence has 
nearly exhausted itself. On first — 
introduction the liquid air may be 
quite agitated and steam may ap- 
pear escaping from the neck. 

On dropping liquid air into a flask of water, the 
action is very violent. The air at first is lighter 
than water, but it grows heavier as it loses nitrogen. 
It sinks, after a little, partly gasifies, floats up, and 
forms ice about itself, and at last disappears. A 
larger vessel of water than is indicated in the cut 
may be advantageously used. 
The small cut gives an almost 
conventional representation of 
what occurs when liquid air is 
poured into a narrow-necked 
flask of water. Inthe actual 
experiment, which is best per- 
formed in a wide-mouthed bottle 
of water, there is much agitation 
and disturbance. The globules 
# rush about, vapor forms about 
me? the mouth of the vessel, and 


328 LIQUID AIR AND THE 


the appearance which is so well presented in the 
cut below is seen. | 
Many substances are made brittle by immersion 


By courtesy of McClure’s Magazine. Copyright, 1898. by The S. S. McClure Company, 


Liquid Air in Water. 


in liquid air. Wehave seen that lead becomes elastic 
and that the pitch of a tuning fork is raised by im- 
mersion. It is quite possible to make a tuning fork 


LIQUEFACTION OF GASES. 329 


out of soft metal which will become resonant on 
immersion for a few seconds in liquid air. A tin dip- 
per after a few minutes’ immersion becomes almost as 
brittle as glass and is broken by a blow. 

India rubber, such as children’s balls are made 


of, becomes almost as brittle as glass after floating 
a few minutes in it. The cut showing a ballin 
liquid air brings out another point of interest—the 
formation of the cloud of moisture and its descent. 


The air which volatilizes from the liquid air is very 
cold and pours over the top of the vessel like water 
and carries the cloud with it. The cloud is com- 
posed of moisture condensed from the outer atmo- 
sphere. 


330 LIQUID AIR AND THE 


The freezing of an alcoholic liquid gives a good 
proof of the low temperature of liquid air. Liquid 
air is poured into a glass of whisky or alcohol, and 
the liquor freezes. The cut shows a sort of icicle 


By courtesy of McClure’s Magazine. Copyright, 1898, by The S. S. McClure Company 


Alcohol Icicle. 


of alcohol lifted up on the end of a roa out of a 
glass of alcohol thus frozen. 

A test tube containing liquid air is placed in a 
glass of whisky. The latter is soon frozen solid, 
and can be lifted out of the tumblerinalump. On 
standing a few minutes after the air has evaporated, 


a 


& 


LIQUEFACTION OF GASES. 331 


the test tube can be taken out, and a sort of tumbler 
whose material is frozen whisky is 
produced. 

Mercury is often frozen by liquid 
air as an example of its frigorific 
power. The experiment as shown 
in the cut consists in freezing a bar 
of mercury in a mould by immers- 
ing it in liquid air. Screw eyes 
are frozen into the ends of the bar. 
A heavy weight is sustained. A 
striking presentation of this experi- 
ment has been effected by a man 


hanging from such a bar of mercury. 
Another example of the effect of cold 
upon mercury consists in making a 
tuning fork out of it. It is easy to 
see that the changes which may be 
rung upon this phase of low tem- 
perature are very numerous. 
Another experiment consists in 
casting a hammer head out of mer- 
cury. A mould is prepared with a 
handle thrust into it, and mercury is 
poured in. Liquid air is poured 
upon the mercury. After a few min- 


53" 


LIQUID AIR AND THE 


utes’ standing the mercury freezes so hard that it can 
be withdrawn from the mould, and a nail can be 


driven with it. We are not 
aware that a mercury nail has 
ever been driven into wood. 

The gasification of liquid air 
is nearly irresistible in the pres- 
sure it produces when confined. 
A quantity is poured into a metal 
cylinder closed at the bottom 
and a plug of wood is driven 
into the top. In a few seconds 
the plug is expelled as if by the 
explosion of gunpowder, with a 
loud report. 

If a piece of paper is saturated 
with liquid air and lighted, it 
burns with much energy. The 
longer the liquid air has been 
kept, the more violent is the 


LIQUEFACTION OF GASES. 333 


combustion. The standing of the air causes it to 
grow richer in oxygen. A piece of boiler felt, which 


ordinarily cannot be made to burn, if saturated with 
liquid air rich in oxygen, burns most brilliantly, and 


if liquid oxygen is used, almost explodes. This is in 
the air. If confined, a violent explosion ensues. 


a 


324 LIQUID AIR AND THE 


An electric light carbon brought to a red heat and 
plunged into the liquid burns beneath it. The car- 
bon dioxide formed by the combustion remains in 

great part in the liquid, freezes 
_ solid and sinks to the bottom. 
A steel pen or a watch 
spring can be burned in liquid 
air-which has been kept stand- 
ing a few minutes. A bit of 
sulphur may be placed on the 
end of the steel and ignited to 
start the combustion. An in- 
teresting variation on this ex- 
periment is to place the liquid 
air ina tumbler made of froz- 
en whisky, as_ described on 
page 330. The pen or watch 
spring is burned in this. The white heat of the burn- 
ing pen, the intense cold of the air, and the alcoholic 
liquid hard frozen form a set of incompatibles which 
it would be hard to equal. The 
combustion of steel, a metal once 
supposed to be incombustible, is 
occurring more vividly than that 
of the most familiar inflammable 
substances and in a vessel made 
of a frozen liquid once supposed 
to be incapable of congeal- 
ment. The material of the pen 
is practically that out of which 
grates and stoves are made. The material of the 
tumbler is approximately one-half alcohol, which lat- 
ter liquid has long been used to prevent freezing. 


pi 
i , | 


| 
i 


LIQUEFACTION OF GASES. 335 


A kettle of liquid-air placed on a cake of ice boils 
actively because of the heat of the ice which supports 


it.) li. the boiling «is. not 
rapid enough, it may be 
accelerated by adding ice 
water or even a lump of 
ice to the kettle. <his 
shows that ice is hot. 

If carbon dioxide gas 
is directed by a jet upon 
liquid air, it is liquefied 
and also forms carbon 
dioxide snow. 


B26 LIQUID AIR AND THE 


But far more impressive than this is the experi- 
ment illustrated in the diagram, which is self-explana- 
tory. <A tube of liquid air is connected to an air 
pump and exhausted. The cold is so intense that, 
after a few minutes, liquid air drips off the outside of 


To Vacuurn Pump 


Rubber 
4 otonper” 


RS 
S 
Liquid Air AOE: be 
Boiling Violently --- 4S 
pd ecmat Chree: 
% Oe : a) 
i ee wenz 
+ ) f 4 Outside Covered 
Ra Fe ty 4 with Snow 
4 ‘ A) (Moisture inAir) 
‘ ae 
\\ et es 
4; \ \) a if if 
Air Condensea } | y, 
and Dropping '\ | Li 
x 
4 


the tube. This is the air of the atmosphere reduced 
to the liquid state by the intense cold of the tube, 
due to the boiling of the air within it. 

The phenomenon reminds us of Dewar’s experi- 
ment with liquid hydrogen, whose cold was so 
intense that it liquefied the atmospheric air. It is 


ov - 


LIQUEFACTION OF GASES. Sys 


also useful in bringing before us the dependence of 
liquefaction upon temperature and its independence 
of pressure. 

Oxygen was discovered to be diamagnetic by 
Faraday. A tube with outlet is filled with liquid 
air and is suspended by a thread as shown. A pow- 


erful magnet attracts it as if it were a bar of iron or 
steel. 

This is an incomplete presentation of the experi- 
mental side of our subject. Changes in colors of 
chemicals and many other phenomena can be-shown. 
The description falls far short of the actual witness- 
ing of the experiments. 


338 LIQUID AIR AND THE 


CHARTER xXVi1, 


SOME OF THE APPLICATIONS OF LOW 
TEMPERATURES. 


Frigotherapy—The frigorific well—-Pictet’s experiment— 
Effects of the first trial of the system—Medical uses of 
liquid air—Critical point as test of purity of chemicals— 
Purification of chemicals by low temperature crystalliza- 
tion-——Low temperature distillation—Regulation of chemi- 
cal reactions by cold—Liquid air explosives—The princi- 
ple of their action—Liquid air in electric power trans- 
mission—Ljiquid air as a reservoir of energy. 


Prof. Raoul Pictet has during the last few years 
given much attention to the uses of the intense cold 
produced by the application of liquefied gases. The 
purification of chemicals, the testing of the same for 
minute quantities of impurities by intense cold and 
by the observation of the critical point, and the 
regulation of reactions, are included in the scope of 
his work. Another of the uses to which he pro- 
posed to put the application of intense cold is the 
treatment of disease. 

He conceived the idea that simple exposure of the 
system to a very low temperature for a short time 
might be productive of important effects. The 
human system in the Arctic regions has endured 
very low temperatures without any effect upon the 
personal hygiene as far as discernible; but it re- 
mained to be seen whether, by descending far below 


a 


LIQUEFACTION OF =GASES. 339 


these natural extremes, a constitutional effect could 
not be produced. 

He constructed what he termed a frigorific well, a 
small chamber, double walled, and lined with thick 
non-conducting material, to protect the subject from 
contact with the walls or floor. Such well was 
about 6 feet deep and 2 feet in diameter. By use of 
the cold derived from the /iguzde Pictet (page 169) 
the temperature within the well could be reduced to 
—110° C. (—166° F.) A foot stool was placed upon 
the floor. This was so arranged that the patient 
could stand upon it, with his head in the open air. 
A woolen cover was thrown over his shoulders, so 
that the head alone emerged, and the rest of the per- 
son was immersed in the chilling atmosphere as if in 
acold bath. The clothing was not removed. The 
chill penetrated it readily. 

The effects of the immersion were very marked. 
The body had to maintain its heat, and this can only 
be done by a more vigorous process of oxidation. 
As Prof. Pictet expresses it, the body ‘becomes auto- 
phage or self-devouring. The temperature taken by 
a thermometer in the mouth rises in amount from 
0°2° to o'9° C. (0°36° to 1°6° F.) The temperatures of 
the human body, it will be remembered, are always 
expressed in this country in Fahrenheit degrees, so 
that the above temperatures are expressible as 
98:76°—-100° F., taking 98°4° F.° as the average human 
temperature. 

A slight feeling of epigastric constriction is some- 
times felt by the subject, a slight momentary paraly- 
sis in the lower extremities may be experienced, but 
all is quickly succeeded by a feeling of general in- 


340 LIQUID ALK AND THE 


vigoration. A reaction generally occurs before the 
patient leaves the well. 

After a while the temperature falls below the 
normal, and a slight vertigo may appear and the 
pulse may slacken. 

A two hours’ exposure proved fatal to a dog. 

Pictet himself reports that in his own case he 
effected a remarkable cure by the use of the cold 
well. He had suffered for years with stomach 
trouble of the dyspeptic type, and resolved to try 
the effect of extreme cold upon himself. His respir- 
ations were at the rate of fifteen and one-half per 
minute; his pulse beat at a frequency of sixty-three. 

He descended into the cold well, wearing a heavy 
wrap. A plank lay upon the bottom for him to 
stand upon. In order to keep in motion, he lifted his 
feet successively six inches high, witha frequency of 
forty-two per minute. For four minutes no especial 
sensation was experienced. After five minutes, or 
thereabout, an indefinable sensation was felt, and a 
desire for nourishment appeared, marking the begin- 
ning of what he terms a frigale. The pulse beats 
rose in frequency to sixty-seven per minute, and the 
respiration to nineteen. Each respiration was deeper 
than usual. 

After eight minutes’ exposure he emerged, feeling 
a sort of prickling sensation all over the body, but 
no cold affected the skin. A well defined hunger 
‘was present, almost disagreeable in its craving ef- 
teres 

On walking homeward, after two or three min- 
utes a reaction set in, exceeding in intensity that due 
to acold bath. The body seemed penetrated by a 


LIQUEFACTION OF GASES. 341 


myriad of fine needles. He states that this expres- 
sion gives but a feeble idea of the physiological con- 
sequence of the restoration of the normal circula- 
tion. The reaction lasted at least fifteen minutes. 

This was on February 23, 1894. He states that 
on that day, for the first time in six years, he ate a 
full meal with enjoyment. 

During February and March of that year he made 
eight experiments in the descent into the cold well. 
The periods varied from eight to eleven minutes 
each. The same sensations and reactions accom- 
panied each trial. He gained weight rapidly after 
the treatment, and found his health radically im- 
proved. 

In the year 1895, at Geneva, Pictet was invited to 
exhibit his work before the National Exposition. 
Among other things, he installed two cold wells 
which could be brought to a temperature of —110° 
C. (—166° F.) 

The apparatus was placed in charge of two physi- 
cians, Drs. Cordes and Chossat. 

The wells were thoroughly protected by fur. 
They were entered by a ladder or the patient was 
lowered into them by ropes. Footstools of various 
height were provided, so that patients, whether tall 
or short, could be properly immersed. A woolen 
covering was provided for the shoulders. 

The working temperature rarely rose above 
—go° C. (—130° F.), and was often much lower. 

It became quite the fashion to take a cold air bath. 
So many presented themselves that the physiological 
examinations were somewhat restricted. The desire 
on the part of the management, however, was to 


342 LIQUID AIR AND THE 


facilitate the trial.of the cold air wells by as many 
patients as possible. 

The patients were examined carefully in many 
cases; the temperatures were taken before and after 
an exposure of ten or twelve minutes. In a few 
instances the exposure exceeded fifteen minutes. 
Some visitors descended only once, others a dozen 
times. 

Full reports on the subject will be found in Sczence 
Francais of November 6, 1896, and a report was pre- 
sented to the Medical Academy of Paris by Dr. 
Cordes at its meeting on October 29, 1897. Finally, 
a most elegant presentation of the subject is given in 
Prof. Pictet’s book “ La Frigothérapie, ses Origines, 
son But,” Paris, 1898. Curves indicating the changes 
of pulse frequency and of temperature, with other 
observations for ninety-seven cases, are given. 

A method of quickly applying frigotherapic 
treatment locally is due to Dr. Ribard. He uses 
solid carbon dioxide alone or mixed with ethyl 
chloride as the source of cold. This he applies 
locally to the skin, protected by felt. 

Dr. G. Fish Clark, of New York, writes that he 
has removed cancer, certain forms of bunions, corns, 
warts and superfluous hair by means of this agent. 
The tissue, when the air has thoroughly worked 
upon it, is practically cut off by means of a tempo- 
rary status in the circulation of the blood, The cir- 
culation is not renewed if a certain amount of care, 
obtained by experience, is taken, as may be indicated 
in each individual case. The parts beneath the mor- 
bid tissue or morbid growth not affected by the low 
temperature of the liquid air are held intact, and use 


—— 


LIQUEFACTION OF GASES. 343 


their circulatory system by means of anastomosis and 
returning of arterial blood (after it has become deox- 
idized) to the veins by means of infiltration through 
the interstitial spaces. This process forms a new 
skin surface under the morbid and frozen surface. 
The result is an upheaval of the super-tissue, which, 
as it dries and shrinks, eventually falls off like a scab. 
The process of applying must be studied, and it is 
dangerous to place it in inexperienced hands, as the 
freezing of vital organs, the danger of involving large 
distributing arteries and veins, and the involvement 
of osseous tissue, must be avoided. It must be de- 
termined accurately by the physician how deep an 
application is going in a certain interval of time. 
From his own observation, he has failed to draw 
the same conclusion as to its effect upon bacteria as 
-M. D’Arsonval, Paris, has arrived at. He has, as far 
as he has investigated, found an utter destruction of 
microscopic life. He has not, however, experimented 
with the bacilli D’Arsonval used. He affirms that 
he has the greatest faith in liquid air as a means 
whereby humanity will receive great aid, and that in 
many cases where the knife is now used this agent 
will be found a most welcome substitute. The pain 
in its application is at no time sufficient to require 
an anzesthesia, it is complicated with no hemorrhage, 
and the patient, after its proper application and 
dressing, feels no additional inconvenience. ‘If by 
inventing this process of manufacturing liquid air 
Mr. Tripler has accomplished nothing else than this, 
his name will be treasured at least in medical his- 
tory as that of one of its most valued contributors.” 
Pictet has applied a curious observation which he 


344 LIQUID AIR AND THE 


made in determining whether chemicals are pure. 
He found that an infinitesimal amount of impurity, 
while it affected the boiling point very little, would 
make a difference from ten to sixty times as great in 
the temperature of the critical state. 

An apparatus was made by which a group of tubes 
of various liquids could be heated to known tempera- 
tures under observation. The disappearance of the 
meniscus was taken as indicating the critical state, 
which was supplemented by the nebulous effects 
which occur at the same point. 

To chloroform were added a few drops of alcohol. 
The boiling point was barely affected, but the critical 
temperature was changed several degrees. A num- 
ber of other chemicals were tried with analogous 
results. For a certain class of substances, therefore, 
a delicate test of purity-exists in the determination 
of the critical point. 

The great degree of cold which the liquefaction of 
gases puts in the chemist’s hands extends an old 
time method of purification to new fields. For gen- 
erations past crystallization has been the great agent 
in purifying salts. If a chemical salt is dissolved in 
water and the solution is evaporated down until it 
becomes a relatively strong one, a point is often 
reached at which the dissolved substance tends 
to separate. With the majority of salts this point is 
attainable. If the strong solution is left to stand, 
the salt will gradually separate in crystalline form. 

The phenomena above described in a few words 
naturally do not occur with all substances, not even 
with all soluble substances. Again, the phenomena 
are not restricted to solutions in water; they may 


LIQUEFACTION OF GASES 345 


occur with other solvents. But water is the great 
solvent, and we are more familiar with crystalliza- 
tions from water than from other substances. 

In all nature there is no more wonderful example 
of mathematical exactitude than that supplied by 
the laws of crystallization. The forms of the crystals 
are based on exact laws formulated originally by 
the Abbé Hauy. 

The fact that a crystal is an exact, mathematically 
determined form almost implies that when a sub- 
stance forms a crystal it must be a pure substance. 
If the substance dissolved were dirty and impure, 
crystallization, should it occur, would have at least 
a tendency to purify it. 

An impure substance is dissolved in water, is crys- 
tallized therefrom, the crystals are removed and 
drained from the liquid—imother liquor, it is called 
—and are found to be much purer than was the orig- 
inal substance. They may be redissolved and re- 
crystallized, when the second crystallization will 
impart a still higher degree of purification. 

This process has long been employed by chem- 
ists and manufacturers to purify salts, and is still 
the great process used to obtain pure chemicals. 

When water is exposed to cold it solidifies, and its 
solidification is a species of crystallization, although 
the crystalline formation is, as a rule, not visible. It 
is brought to view by melting ice under proper con- 
ditions, and all are familiar with the beautiful crys- 
‘talline forms which are discernible in snowflakes. 
We should expect, therefore, that the freezing of wa- 
ter would have a purifying effect upon it. 

It has this effect. Ice is purer than the water from 


340 LIQUID AIR AND THE 


which it is made. If cider is exposed to cold, the 
water freezes out in a relatively pure condition, and 
the cider is left asa sort of mother liquor, so much 
stronger than before that. what is almost a brandy 
results. Here the cider constituents are the impuri- 
ties, and they are left in the mother liquor in greatly 
concentrated condition, and the water is crystallized 
out as ice in a relatively pure state. 

Water is ordinarily purified by distillation. It 
would be perfectly practicable to purify it by re- 
peated freezings, if distillation could not be effected. 

Liquefied gases, by their innate cold and power of 
absorbing heat energy or rendering heat latent, ex- 
tend the range of the freezing processes to new fields. 
Liquid air can solidify and thereby purify alcohol. 

A number of very important chemicals can be puri- 
fied by intense cold. One of the most familiar of 
these is chloroform. Used as an anesthetic, it is un- 
certain how much of the bad effects of chloroform 
are due to its impurities. Irrespective of any dan- 
ger to life, there are after effects which it is desirable 
to overcome or minimize. The purer it is, the less 
are these after effects, and it is quite possible that 
with absolutely pure chloroform, deaths of patients 
from the effects of its administration would be far less 
frequent than they now are. 

Chloroform is purified by freezing. On subjection 
to a proper degree of refrigeration, the pure chloro- 
form crystallizes out almost like sodium sulphate 
from water. The very cold crystals are removed 
and melt, and an extremely pure product is the re- 
sult. The process is termed one of rectification at 
low temperature, and can be applied to a number of 


LIQUEFACTION OF GASES. 347 


liquids. Chloroform is taken as a typical substance, 
and as one for which a great demand exists. Ether 
is another chemical product which is thus purified 
with success, and alcohol can be purified by the 
freezing process until it is 100 per cent. pure, or is 
what is known as absolute alcohol. Various anzs- 
thetics are purified by freezing. 

Formerly these methods were inapplicable, simply 
because the degree of cold requisite for their execu- 
tion was unattainable. 

Distillation by heat is attended with the objection 
that the heating may impair the product. Low tem- 
perature distillation is made practicable by utilizing 
the intense cold of liquefied gases to condense the 
distillate. In this way so high a vacuum is produced 
that a liquid will distill with relative rapidity at ordi- 
nary temperatures. It is a reversal of the ordinary 
course of operations. Instead of applying heat to the 
retort and forcing off the gasified liquid against the 
pressure of the atmosphere, the latteris removed and 
the gases which take its place are condensed by in- 
tense cold, so as to maintain an almost perfect vacuum 
over the liquid, which distills without artificial heat. 

Chemical reactions are so greatly modified by 
temperature that the cold of boiling liquefied gases 
may bring about radically different results in these 
cases. Thus, if organic substances are treated with 
nitric acid, the products will vary according to the 
temperature at which the interacting substances are 
kept. - As illustrations of compounds produced by 
the action of nitric acid on organic substances, nitro- 
glycerine, guncotton and many similar substances 
may be cited. These have extensive uses as explo- 


348 LIQUID AIR AND THE 


sives, and by deoxidation give a host of products such 
as the aniline dyes. Any process which affects these 
reactions would affect the most important field of 
chemical industry. Heat, in the popular sense, has 
hitherto been the great agent in producing chemical 
reactions and in modifying them. Intense cold may 
now be looked on as a supplementary agent. 

An explosive is a substance whose action may de: 


pend upon various chemical and physical actions.. 


If two volumes of hydrogen are mixed with one 
volume of oxygen, a colorless mixture of gases re- 
sults. If an electric spark or other source of heat is 
applied to the mixture, they at once combine sud- 
denly, and with production of great heat. The re. 
sult is an explosion, and the operation of combina: 
tion produces a sound like a pistol shot. The mix. 
ture can be made to discharge a shot from a gun or 
to blast rocks. 

Another class of explosives mgs by simple 
breaking up of a feeble chemical combination. Chlo- 
rine and nitrogen can be made to unite and produce 
an oily liquid—a chemical combination of one atom 
of nitrogen and three of chlorine. On the least dis- 
turbance, or without any apparent reason, the com- 
pound will explode, simply reproducing chlorine and 
nitrogen. But, simple as it seems, the explosion is 
of fearful violence, and it is truly appalling to read 
of Davy’s and Faraday’s work with this substance, 
one of the most dangerous known to humanity. 

It is unnecessary to go further. When a substance 
can be made in which a very violent chemical action 
can be induced, the heat produced and the changes 
in volume may be so sudden and great that an ex- 


+ aa 


LIQUEFACTION OF GASES. 349 


plosion results. Such a substance is termed an ex- 
plosive, and there are a great many of such now in 
service. | 

One of the proposed uses of liquefied air is as a 
constituent of an explosive. If air is liquefied, it 
occupies about one eight-hundredth of its former 
volume, so that there is involved in its liquefaction a 
concentration of its oxygen to that extent. Then, 
we know that, by standing, the nitrogen evaporates 
more rapidly than the oxygen, so that a constant 
action of enrichment in oxygen is taking place as re- 
gards the unevaporated liquid. Thus, the liquefac- 
tion of air and subsequent enrichment may amount 
to a concentration of its oxygen of sixteen hundred 
or more times. 

Even this is not so remarkable as it might seem. 
We are very familiar with oxygen in liquid and 
solid form in combinations of the chemical order. 
Thus, water, which we know most familiarly as a 
liquid, or as a solid, contains eight-ninths its weight 
of oxygen. Startling as it seems, it is no paradox to 
say that water is approximately pure liquid oxygen. 
This assertion would be based on its chemical com- 
position by percentages or proportions by weight. 

But there is more than this to be looked at. By 
its affinity for hydrogen it is locked fast in the water 
molecule, so as to be comparatively inert. Those 
who have seen the fierce combustion produced by 
soaking organic matter in liquid air and then igniting 
it would never think of employing it as a material 
to put out fires. Yet we use water for this purpose, 
although it is far richer in oxygen than is liquid air. 

Under certain conditions water can support com- 


350 LIQUID AIR AND THE 


bustion. If steam is passed through a mass of red 
hot copper borings, iron borings, coal and many 
other substances, it gives up its oxygen to them, the 
hydrogen severs its alliance, and a true combustion 
ensues at the expense of the oxygen of the water. 

It is hard to bring about a combustion in water 
vapor, and in liquid water it is all but impossible, 
owing to its cooling powers. 

The air we breathe contains about one-fifth of its 
volume of oxygen, and fires burn in it with far 
greater energy than in steam, which contains one- 
third its volume of the same gas. This is because 
oxygen in air is free and uncombined, and can unite 
witn anything that claims it, without having to dis- 
solve any bonds which unite it to other elements. 

We are familiar with oxygen in the solid state in 
innumerable compounds. For purposes of com- 
bustion and explosion, we select those that are rich- 
est in oxygen and which have it most feebly united 
or combined. The “villainous saltpeter,” potassium 
nitrate, contains in round numbers 48” per cent. 
by weight of oxygen, which is very feebly com- 
bined, and is, therefore, so ready to combine with 
carbon, sulphur and other compounds that for cen- 
turies it has figured as an ingredient in the great ex- 
plosive gunpowder, which has ended many a life on 
the battlefield, a service some may be weak enough 
to consider of very questionable utility. The sci- 
entist cannot but consider the human body as a 
very exquisite mechanism, and must regard its de- 
struction by one who cannot adjust and create its 
mechanism as a work opposed to every ethic of true 
science. Science always contains for its true vota- 


LIQUEFACTION OF GASES. 351 


ries elements of admiration and wonder. Destruc- 
tion of that which cannot be created or resynthe- 
_sized is an abject confession of weakness that should 
be most discordant with every note of the scientific 
student’s nature. 

Now take liquid air which by standing has become 
rich in oxygen. It is liquid and of about one-third 
the specific gravity of typical solid oxygen-contain- 
ing compounds. One-half of its weight may be oxy- 
gen which is absolutely free and uncombined, ready 
on provocation to unite with many elements without 
having any bonds of union to sever. It is evidently 
an available substance for a constituent of an explo- 
sive or for an inciter of violent combustion. 

It is found that if liquid air, after standing a little 
while, soas to evolve nitrogen and become rich in 
oxygen, is poured upon organic matter, such as cot- 
ton, felt, powdered charcoal and similar substances, 
a violently combustible product is formed. A piece 
of heavy felt which can hardly be induced to burn in 
the open air, when soaked with liquid air, burns 
with the brilliancy of a piece of pyrotechnics. 

This is combustion. Rapid combustion is explo- 
sion, and with such mixtures explosion can be 
brought about by confinement before ignition and 
by ignition with a detonator. The shock and heat 
set the whole off at once, and an explosion compara- 
ble to that of gunpowder results. 

The following are the general features of Dr. 
Linde’s practical trials of the liquid air explosive for 
blasting rock and coal: Charcoal is broken up into 
grains about the coarseness of beach sand. The 
effect of pouring liquid air upon the porous mass 


352 . LIOUID ATRAAND Crh 


with its many points is to eliminate the spheroidal 
state and to provoke violent ebullition. This would 
be so great as to scatter the charcoal to right and 
left. Accordingly, to keep it together, the charcoal 
is mixed into a sort of sponge, with one-third of its 
weight of cotton (cotton wool or waste). 

Liquid air, which has stood long enough to con- 
tain about half its weight of oxygen, is poured upon 
the mixture of wool and charcoal. An ebullition at 
first occurs, during which more nitrogen than oxy- 
gen goes off, and afurther concentration of oxygen 
is effected. The moist mixture is rapidly charged 
into insulated paper cartridges, and is ready for use 
within five or ten minutes. It must beat once placed 
in the shot holes and exploded by a detonator, pre- 
ferably an electric one. But any detonator which 
can be rapidly exploded will answer. Delay is fatal 
in one sense—it destroys the efficiency of the cart- 
ridge. After fifteen minutes to half an hour the 
liquid air will have so completely SAD OA gS that 
no explosion can be produced. 

This might,seem a defect, but it is quotedgasea 
merit. Countless accidents have happened in mining 
and tunneling operations from cartridges hanging 
fire, as it is called, in blast holes, only to go off unex- 
pectedly, and killing and maiming the workmen. 
Half an hour after a liquid air cartridge has been 
placed in the hole it is innocuous. 

By using air which has stood a longer or shorter 
time, the power of the explosive and the heat pro- 
duced in its explosion can be controlled at least to 
some extent, even if it must be considered largely 
guesswork. 


LIQUEFACTION OF GASES. ane 


The explosive was used for several months in a 
coal mine at Pensburg, in Bavaria, near Munich, 
with good results. Where power costs nothing the 
explosive is a very cheap one. In tunneling opera- 
tions it often happens that there is a surplus of 
power derivable from streams that flow in the 
vicinity. The European engineers show a great 
aptitude for utilizing such sources of energy. 
Where such are available, this would be the cheap- 
est possible explosive, as well as the safest. 

In America, Tripler has experimented in this di. 
rection, and has found that he could blow heavy 
steel tubes open as if with dynamite. 

Elihu Thomson presents the possibilities of liquid 
air in electric power work. Few realize how large | 
an item capitalization plays in the problem. The in- 
stallation of a long line of copper is an expensive 
matter, and successful efforts are made to reduce 
it by employing high potential difference. But 
could the temperature be reduced to that of liquid 
air, a thin wire would carry a large current at rela. 
tively low potential difference, or at the high poten- 
tial difference a very much largerone. As far as the 
cost of copper went, the capitalization of the line 
would be slight, in proportion to the power trans- 
ferred. There would be every excuse for an expen- 
sive construction of a line which would carry a 
large current. The capitalization per unit would be 
quite small. 

The idea of Elihu Thomson is expressed by refer- 
ence to the power of Niagara Falls. An expensive 
power installation is there established which works 
to its full capacity for only a little over one-third of 


354 LIQUID AIR AND THE 


each day. He suggests that the power might be 
used during the night hours for making liquid air 
which could be stored in tanks well insulated from 
the outer air temperature. The inevitable evapora- 
tion of air could be utilized to perfect the heat in- 
sulation by being led down through the jacketing 
of the tank. 

A furnace in a steel works or other industrial es- 
tablishment may have a temperature on its hearth 
and working chamber of two or three thousand de- 
grees above that of the air, yet there is no difficulty 
in insulating it by a firebrick lining and, perhaps, 
ordinary brick exterior,so that the hand can be 
placed upon the outer surface without being burned. 
Between liquid air and the atmosphere there is but 
one-eighth the difference of temperature that exists — 
between the heat of a furnace and that of the air. 

The copper conductor could be inclosed in a pipe 
which could be kept cold with liquid air. Such a 
line need not involve a loss in the energy trans- 
ported of more than one or two per cent. In most 
long distance lines a loss of ten or fifteen per cent. 
of the energy is allowed for. It is possible that 
the saving of most of this might pay for the cost of 
liquid air, irrespective of the increased capacity of 
the line. 

A few years ago it would have seemed absurd to 
make such a suggestion. But there is not a particle 
of absurdity init. The achievements in the produc- 
tion of liquid air by Tripler and others, and the 
carrying of it hundreds of miles by rail in jacketed 
buckets, show how easy a substance it is to handle, 
once a sufficient quantity is brought together. 


LIQUEFACTION. OF GASES. 355 


The surfaces of solids of identical shape vary with 
the squares of their linear dimensions. Thus, if there 
are two of Tripler’s air buckets exactly alike, except 
in size, and if one is twice as large as the other, the 
surface of the tin and of the open top will be four 
times as large in one as in the other. The volume 
varies as the cube of linear dimensions. Therefore, 
in the case cited, the larger bucket will hold eight 
times as much liquid air as will the smaller one. 
Therefore, if we state the relation of surface to 
volume in the small bucket as a: 4, the ratio in the 
large one will be 4@a:8 06. That is to say, there will 
be half as much surface exposed in proportion to the 
contents in the large bucket as in the small one. 
The heating and wasting of the air by evaporation 
is due to the surface exposed. Therefore, the larger 
the vessel, the less in proportion will the waste due 
to heating from the exposed surface be. If a bucket 
were five times as large, the ratio would be still 
more favorable—25 @:125 6, or 1:5, and so on. 

By carrying out what the French would call the 
audacious idea of making liquid air by the barrelful, 
Tripler has demonstrated the possibility of handling 
it on the large scale pretty nearly as water is hand- 
led. The English scientists, as late as 1897, find it im- 
possible to credit the accounts of what is done in this 
country. Prof. Fleming says that “nothing was 
_ effectual in storing liquid air until Prof. Dewar in- 
vented the silvered, vacuum-jacketed glass vessel 
as a container, and the even more effective and in- 
genious mercury vacuum process for introducing 
the high vacua required, without which none of our 
research work could have been done.” This is not 


356 LIQUID AIR. 


the only quotation which might be used to show 
how incredible the achievements on this side of the 
ocean seem to foreign investigators. 

{ Liquid air, if it could only be produced cheaply 
‘enough, would represent an ideal substance for the 
production of energy. It is calculated that in one 
pound of it there are stored 139,100 foot pounds of 
energy. An electric storage battery varies from one- 
tenth to one-twentieth of this amount per pound of 
its own weight, and compressed air is about one- . 
tenth. A pound of water compressed to 400 pounds 
pressure to the square inch has only one-quarter 
the energy of an equal weight of liquid air. In the 
compressed air and liquid air calculations the 
weight of the reservoir is not included. 

The peculiarity of liquid air as a material for the 
storage of energy is that it can be made to give any 
pressure, from the slightest up to many atmospheres, 
nearly a thousand in number. It represents the 
water in a boiler, the containing vessel is the boiler, 
and the atmosphere represents the hot gases and 
flames of the furnace. By exposing more or less of 
the surface of the vessel to the air the evaporation 
could be controlled. Its expansion would tend to be 
adiabatic, but by further use of an air reheater, | 
identical in construction with an air condenser, the 
disadvantageous adiabatic element may be sup- 
pressed, and isothermal, or nearly isothermal, ex- 
pansion substituted. The condition is as if steam 
were superheated between boiler and engine, and as 
if the engine itself were heated by an external fire. 


Oo ON AN FW NH 


= Ss eS 
Si) asi So 


H 
Ww 


Te ee ed! 
Nun + 


HoH 
on 


H 
Ne) 


SUBSTANCE, 9 
a 
B 
MVERISIP os Sa = yal BOW) 
Hyd. selenide.| HgSe 
Ammonia ....| NH, 
Propane... C3H, 
Acetylene.....| CoH» 
Nitrous oxide] N,O 
FAthamMe tees ee | Coble 
Carb. dioxide | CO, 
OZONE see sen Os 
Ethylene. . CoH, 
Methane .eens| Orla 
Nitric oxide ..| NO 
Oxygen..a.64 Os 
Argon.,... A 
Car. monoxide] CO 
EN dite cece chal vee PAs 
Nitrogen.. Ne 
Hydrogen Ho 
sKVbiverl As, Boga) 8sle 


Critical 
temperatures, 
Degs. | Degs. 
Cent |ebali: 

365 689 
138 280°4 
130 266 
97 206°6 
37 986 
35 96 
34 93°2 
31 88 
5) 50 
— 81°8 | —II5°2 
Se OS hehe, 
—118°8 | —181°4 
—I2I —185°8 
= 39"5,.| 219 £ 
—I40 | —220 
—146 —231 
ns i eta 


Temp. of satu- 


PHYSICAL CONSTANTS. 


rated vapor at}, ; 2 Pressure 
Critical atmospheric Freezing point.! ‘at which 
pres- pressure. freezing 
cite point was 
‘ determined. 
Degs. | Degs. | Degs. | Degs. mm. 
Atmos;| Centi a) Habr Cent) |i halt, 
200 100 212 fe) a2 760 
gi — 4I — 41°8| — 68 | — 904 Son 
ve | 38 | | oti tiqluid at 
an ae ill liqjuid a 
4 45 49 —151| ° C. sees 
ae — 85 —I2I — 81 —113°8 950 
75 | 89 \ | =128 re =a175 760 
é ., {Still liq)uid at 
DO) AN 93 leek Sort —151/°C tees 
75 |—80 |—112 |— 56 |—69 760 
cites —-I06 , —1588 aie 
51°7 | —102 —150 —169 —272 birt 
54°9 | —164 —263°4 | —185°8 | —302°4 80 
71°2 | —153°6 | —254 | —167 —369 138 
50°8 | —181°4 | —294°5 munavie 5 On 
50°6 ; —187 —304°6 | —189°6 | —309°3 aseele 
35°5 | —190 —310 —207 | —340°6 100 
39 —I9QI°4 | —312°6| .... Becht BOOS 
35 | —194°4|—318 | —214 | —353°2 60 
20 —243 | —405 ies eed Beck 
Below 
AOE -— 264 —443"2 2 . 


Den- 
sity 
of 
gas. 


2°02 


Density of 
liquid at 
temperature 
given. 


rat 6-426. 


0°6364 
atom Ce 


Data collected and tabulated by Walter H: Dickerson, M.K, 


1 
J 


Color of 
liquid. 


Colorless. 


“ae 
ce 


ac 
«6 


ae 


66 


Dark blue, easily 
exploded. 
Colorless. 
ae 


ce 


Blue. 


Colorless. 


oe 


Light blue. 


Colorless. 
e 


uv 


oy 


hed 


INDEX. 


Absolute cold.... 
Absolute zero. 
Acetylene, Cailletet’s work on, 

175, 179-181, 182-183 
Adiabatic expansion and contrac- 


ss ee eetesee +s 


19-20 


TiOiete ee bee eat Re ets an 69 
Air, 2. CONVEYOE-OL Heat” 2)... vess.c 244 
Air and water contrasted......... 85-86 
Air, Cailletet's liquefaction of ..186-187 
AGT COMPOsitiGn:Olr ee -sese eee hei 87 
Air, constancy of composition of . 89-90 
Air, dry and wet compared...... 14-15 


Air, experiments with liquid. ..325-337 
Air, how to preserve liquid indefi- 


MNICELY oe ee tence score . 260-261 
Air, liquefied, giving two liquids 220 
Adar, liquid, defined..:...... De. Stee biel 9 
Air of atmosphere not a chemical 

COMIDOUNC 45 NEN ae ay ae ie alae 86-87 
Air, physicists’ and chemists’ 

views of Ee 88-89 
Air, Wroblewski’s experiment on 

Hieivetactioniol asses wre eee 220 
Alcohol frozen by liquid air.... ... 330 
Alcohol frozen by Wroblewski and 

OISZEWSKIZA coe pares cs 212 
Jagecvehedsh dk Aah eS Raa eee eed 7, 
Ammoniacal gas, Faraday’ Ss ie 

PACIIOM Olmeen pene «cee a ties III-I12 
Ampere and Colladon, anecdote 

OL ee eaten eee Ee. cme eine 133-135 
ASIGECEL eee te mee) Garters anaes 214 
Andrews, memoir on We of, by 

atte articles Ovaries aa. . 5 comers 150 
Andrews, Thomas.19, 133, 147-150, 

169, 176 
Apparatus and experiments, Cail- 

letet’s liquefaction.......... 177-182 

Apparatus and process, Trip- 


ler’s .. 


Apparatus, Hampson’s, for lique- 


EVATIOVAIE army cae e ee , 320-324 
Apparatus, Linde’s, for liquefying 

BAG See mne bs, Sie Ga Ao wares thier 307-319 
Apparatus, Pictet’s liquefaction. 157-163 
Apparatus, Thilorier’s......... 137-141 
Argon. See italic ere lesan Taher aires) satecater’ 87 
Arseniureted edrogen: liquefac- 

RIO OL. inter noek dane weet 122 
Atmosphere, its relation to ani- 

ialsand birds: 5, 22.ees vnc 85-86 
ALMOSpHEereNiguetliedu=a. aces. 336 
Autophage state of human sys- 

Le o0le Amar Rreyepesete Rete cee caer Ratio ance, 
Babbage.. ap «+e LIQ-120 


Barker, eesiee F, gee Aen 240 


Barleycorn as unit of space...... 25-26 
Bath well, helium from..... . «275-276 
Battle of squares and cubes....355-356 
Baucalati: . Bi. se CR ee LS 
BenjamineLnontpsol aes 93 
Bianchi’s modification of Natter- 

ers apparatus: .. 23.2% ee. 142-145 
BlenkerOOdGra ememue. meta et .. 245 
Blenkroode’s experiment  illus- 

(amalernele? UAE TR es oa Mobo dos 245 
Boiling a cooling process......... 76-77 
Boiling by producing a vacuum. 77-78 
Bollinie PASS seem ce eeeticccte scone 76-77 
BOWE Areata clos et ER SEK. Malisveha en: 201 
Brunel’s carbon dioxide engine ...99 
Buckets, Tripler’s, for liquid 

Eby Cone UR ye ete a ede . 289-296 
Bulbs, efficiency OMditerent mrss: 247 
Bulbs, vacuum, mercury silvering 

Ol eee |) asta ee wee. -247, 253-254 
Cacmardideia Outed. 0--.. 128-133 


Cailletet, L. P...22, 24, 58, 135, 150, 
I51, 155, 150, 165, 172-202, 204, 
212, 214, 215, 218, 219, 220, 226 


360 INDEX. 
Cailletet and Hauteville on spe- Coal.as a cheniical ios. .anisese eee Soe 
cific gravity of oxygen.......... 197 >|, Cold) absoluten-seesnaice. tee een 19-20 
Cailletet, honors yeceived by .. -.),.174 | Cold, distillation by 2.22.2 e, ame 347 
Cailletety lie ofgeeee aco: 2173-174 |. Cold, regeneration of) .e-en. afore 
Cgilletet, liquid acetylene, his Cold regenerative process.. .,.....265 
WW OL Ky O11G eee fe ee 197-199. |. Coleinatlrs men eer seek eee ere ears 
Cailletet on conductivity of metals Colladon and ere anecdote 
at low temperatures . .........201 Of Ei caer oi Sieleisieie ste cia vate R LOS 
Cailletet on critical state pheno- Colladon, patel; . 133-137, 174, 176, 
SVEN Fete, onc cate doe ca nie 190-192 179, 200, 207 
Cailletet performs La Tour’s ex- Colladon, his original apparatus... .136 
PELIUIME ME eee raceree side Gaeete 202) || Conservation of energy, ose eeee 29-36 
Cailletet’s cold blast blowpipe, Contraction, adiabatic. 2... sees Oe 
TAT, 168-199 1.) Cordes; Dr. 2.0. os seeiehiee a eee 341 
Cailletet’s continuous liquefac- Count iwiniordiess ee eee eee 92-95 
Lion process ze. acs cet ccaisisieus yeOO na CLitical precsu reqs ams eapteciaie ieieepretie 19 
Cailletet’s control experiment Critical state of anatter,,. son caee 19-20 
with hydrogen inte escalate log Ciiticalitem peratiine anes 19 
Cailletet’s controversies with De- Crookes ayers mse Jisee = |) HOO=BS 
WALT Scale de see eee eee as 232-233 | Crookes layer, protection due to....84 
Cailletet’s frozen mercury stop- Crookes, William seen ee vaio ton 
POL Sirs: cassie ssuemeroae idee ..187 | Cubes and squares, battle of...355-356 
Cailletet’s letter to oem of Cyanogen, liquefaction of, Fara- 
SSeS. soak Age nkc . 183-184 Gay) S 5 hu ycee eermeente wiereie sieie ere efep alee 
Cailletet’s liquefaction of hydro- Cycle of réversible ensine 77... ens 7o) 
SOU ered ae 5 Os oe cannes ..218 | Davy-Faraday Research Labora- 
‘Cailletet’s manometers .... . 187-189 LOLy Ja. thease ee eee II5 


‘Cailletet’s thermometric methods, 
trials Of seroma aioe: 201-202 
Callendat ae metas Rae noes Bok yi 
Carbon  bisulphide, frozen by 
Wroblewski and Olszewski,...212 
Carbon burned in liquid air........334 
Carbon dioxidein air.... .-.....90-9I 
Carbon dioxide in liquid air........336 
Carbon dioxide, liquefaction of, 


Hatad ay |S cceeccn avs Taipdon set, Cote 
Cartpon dioxidensoliduersiest tier 15-16 
Carbon monoxide dispatch, Wrob- 

lewski and Olszewski’s ....... 213 
Catnots Cy clegannats arene ae 70, 288 
Celsius thermometer scale....... 38-39 
Centimeter? avsschs aon so ones eeu 
Chemical reactions governed by 

COld Sites comet sree e tener meses 347=348 
Chlorine, Faraday’s liquefaction 

Ole eee Atay eet Ara. 106, IIO 


‘Chlorine, Northmore’s liquefac- 
tiomofee ee ceded ani pLOO L710 

Clark: "Dit Gaehisihiat..@s aeeee ere 342 

<OLAUISIUGE= Aree aanee Seleissresisie esa treet 24. 


Davy, Sir Humphry.. ...96-99, I02, 
103, 105, IIo, pit. 120 121, 126 


DEDLAY sae eee Sieve s (ae meee Deo ee 
Dewar and Mbiseaas s Tiqueiacare 
of fluorine ...... Serene 276-280 


Dewar, James. .96, 99, 112, II5, I5I, 
157, 168, 198, 200, 206, 215, 219, 
225, 227, 229, 230-285 
Dewar’s apparatus of 1883.... ..... 233 
Dewar’s apparatus of 1895...... 238-239 
Dewar’s bulbs ... ...... he eae 244-254 
Dewar’s bulbs, mercury silvering 
Olt ean tere a eee 00247, 253-254 
Dewar’s colleagues.... ... .... Seren 232 
Dewar’s controversies with Cail- 
ete tee esiedieleiesrialsielelsiole 2522 ae 
Dewar’s early apparatus. ,,....233-237 


Dewar’s gas jet experiments. . . 264-266 

Dewar’s hydrogen jet experi- 
IMLETIUS, «1s cn omni eee fey «200-271 

Dewar’s life ..... « 2 fi enmelets 1231-232 


Dewar's liquefaction of helium, ...28r 
Dewar’s liquefaction of hydro- | 
WEN cio ase Aponon placcucnadcese as: 


INDEX, 


Dewar’s separation of helium. ,275-276 
Dewar’s small gas liquefaction 

AP PAPALUS woe ane. Wetec sees . 241-243 
Dewar’s suggestion of marsh gas 

as a refrigerant..... pases 252-233 
Dewar’s use of Pictet’s cycles.... .233 
iMananeS VES enoees Ghosaer 249-253 
Diffusion aeirdonicness 
Dog killed by low temperature ...340 


SC eC 


Double and triple glass gas 
DULDS een ee ete eine cca eee es 245-247 
PVE CKELE Rac tecielets taie ¢.5 eiaeieres ers 206 
Dufour, Prof. Henri............155~156 
FVGASON ae ms Sacer wie segma set os 2200 
Effects of intense cold on human 
SYSUCIILE Genie setetcteicictalslevessss « © 339-341 
Eiffel Tower manometer .....,188-189 
Elasticity of metals affected by 
ebld- fa EONS S Se ee 255-256, 260 
Electric power transmission, 
hoquidiaira nae eee + 353-354 
Electric resistance of metals 


affected ne cold, Wroblewski 

CI rr sods ck geese tees .»..219-220 
Electrolysis of water .148-149 
Elements, fundamental in physics .25 
Elongation of metals affected by 


Cold ere Shek Uebitis ca vee ae 6259-200 
OSes Meteors Sa were nee eae STORES, 
nervy, atid forces) ae wacccoas 24-25 
Energy, conservation of ......... 29 -36 
Energy converted into useless 

MEAE sates. AR ciao ciound eae eek!) 
Energy, kinetic: 1.5: eee SERA TaN RS 
Energy, low grade heat.. . .288-289 
Energy, low grade heat fae paid 

Alice Mere a tae Nels ote e330 
Energy, potential ....... Aan eter 30 
Energy, reduction of available. ..71-72 
Energy, reservoir of........ ey 2433 


Energy, unutilizable of world. ...34-35 
Energy, waste of, in railroads and 
steam navigation 
tLOpYaieee ne cara ceets Se ese 
ISCO I ce essiee's e's .. 197-199 
Ethylene,. liquid as perigerant: 197-198 
Ethylene, Wroblewski and Ols- 
zewski’s results with. ..212 
Kuchlorine, Faraday’s licuefac- 
TLOMS ODM i uae cet cts 
Evaporation by stream of gas. 201, 214 


C—O 


Expansion, isothermal...... 
Experiment, Blenkroode’s, show- 
ing utility of vacuum . ee ZAS 
Experiment, Count Rumford’s.118-119 
Experiment illustrating conser- - 


VALIOMIOL Cllet Sy ea tnereer saan 32 
Experiment in boiling by a 

MAGGI cons, Veils cele Pepe's < hesagee ee 77 
Experiment, Joule and Thom- 

SONS hele eraeiiners Meise ois ewig OLaO2 


iHxpetiment,, Joules 7 .a..02s5 400 00-02 

Experiment on low grade heat 
CULES Y seicieies siennes 000 0 0 35-30 

Hxperiment with chlorine hy- 


eeeeee 


Grate, crest sede eee Sone cae el 20 
Experiment with india rubber 

Danae eee eee nent eur 
Pcerimicht: Walland Serer coe . 24 


Experiments, Dewar’s yvdnoven 
OU iaran canine eee eale eos Pas. 200-271 
Experiments, Dewar’s, on solu- 
tions of gases in other lique- 
fiedePAaSeS wees eat tetas 271-274 
Experiments, Dewar’s, with gas 
jets 
Experiments, early, of Faraday...103 
Experiments in spheroidal state.82-83 
Experiments, La Tour’s..... . «129-132 
Experiments, Pictet’s, of 1877..160—-161 
Experiments with liquid. air.. .325-337 
Explosions in niet rs and 
Dayy’s early work.. aieierecieLLO 
Explosive, liquid air........ ge ae 
Faraday as fellow of the Peover 
SOCELY x wrest Gir aiers'e seein e lates 106-107 
Faraday, Michael..... 28, 42, 95, 99, 
100-1i5, I17-129, 131, 226, 240 
Faraday, Michael, his life....., 100-115 
Faraday on Davy’s continental 


LOWLseteiolois oiel ce stonister Sonne tee ste 105 
Faraday’s bent tubes........ . .123-128 
Faraday’s death......... ystems pew tlS 
Faraday’s discovery of magnet- 

ism of oxygen..... .. 114-115 


Faraday’s engagement at Royal 


Disk ohgbhalore oe WAG Sens . 104-105 
Faraday’s failures in liquefactions 
OL FaSeSWac ow. sca aes LRP Care Oe II4 


Faraday’s liquefactions of gases, 
106-112, I13-I14 
Faraday’s solidification of gases ..114 


362 INDEX. 
Faraday’sthermometer....... MOCHSCe) Meiniholtza te. Wee Shuaje telat ee one oer 204 
Fleming ays Aus sense see SOR ont 232 Heéeryvyscdeashior peo caer foctaelge 
Fluorine, liquefaction of,......276-280 | Hogarth.... ........ ade meee 28 
HOLCE 75 th jes sem lee cee wake ents 27-29 | Hydrochloric acid, Faraday’s 
FOLCemnds CNeErsy sin nce eee 24-25 liquefaction of..... A ts II2 
Force, conservation of, an errone- Hydrogen, Cailletet’s liquefaction 
ous: docttiie spt eee an 20=29 OLE ere on Oneraenee . 184-185 
Bored, HVine sce ea ees mero oene ...29 | Hydrogen, constants of liquid by 
Formula, Joule-Thomson effect, Olszewski. . ; ; . . 227-229 
300-306 Hydrogen dispitcin a¥roblewsikitst 218 
Frigotherapy........+ Pre 338-342 | Hydrogen, jet process of liquefy- 
Fuller, Mr) ohne i teens eee ier 95 ba ari herr cca . 266-271 
Fullerian professorship in Royal Hydrogen, liquefaction of, De- 
Unis titittOn re tee winner er: 95, 96 Will, Siemyroceisse ieee perestion 280-285 
Gas cooled by expansion ........299 Hydrogen, liquefaction of, Pic- 
Gaseous state of matter.......... Leet? EGE). hg nde Ane ose, uGhiC’ se eeee 164-165 
Gases, boiling. ...4... 2623 Se mite 76-77 | Hydrogen, liquefaction of, Wrob- 
Gases, Davy’s experiments in in- ENV SIGNS yo he eee . 218-219 
Helin. 7.2 caries 97-98 | Hydrogen, Wroblewski and Ols- 
Gases, Davy’s views of the utility zewski’s attempt to liquefy.213-214 
of liquefying....... a ree 98 | Hydrogen, Wroblewski on criti- 
Gases, determining latent heat of calipressure Ofiat sso ae 266 
liquefied,........ aera ..)..261 264 | Ice; Hquid air boiled ont. meas 335 
Gases, determining specific heat India rubber affected by intense 
OiMGiehe des: meee tir & 261 264 Cold ete ree Seay hee .eneeseg 
Gases, molecular motion in...,..17-18 | India rubber band experiment... ..32 
Gases, permanent 1.2 27 oes. 149-150 | Isothermal expansion and con- 
Gases, solution in other liquefied traction. ete. ns . 68-69 
gasess 5 AP ip nhieu. eee. -271-274 | Jamin Sees cosy wpe cia oa) nemne 
Gas heavier than liquid ........ 21 Joules. 25s eee os fase 60, 61 
Gas jets, Dewar’s experiments Joule and Thomson’s experi- 
AALAEY Ape. GeND eh) SAGAOOoS . .264-266 ment..5. | aah owe eae 61-62 
Gas, receiver for liquefied, Cail- Joule’s experiment), 2 60-61 
letet’s joe cielo ect embstem § «+++. 195-196 Joule-Thomson effect ..269-270, 297-306 
Gas, the perfect... ..e0. sseee+e-59-62 | Joule-Thomson effect, negative... 3o1 


Galbanmui Hy, waste eeraelete eet OL 


Galitzine. 35: SOC OSE ATE Ono eens 22 
Grama onc sedorsise ai Mass ta, tae aes 25 
Griffiths. Fonte. So eae ne eteet tee wes 57 
Hampson.....226, 238, 265, 300, 391, 

309, 320-324 
Ha nti yee cicehiarelnele er seals . a2 
Fiautevilie. 4% arti ae eecteer 197 
Heat. latent oes: setae ne ois a 72-76 
Heat, measurement of... ....... 37 
Heat.or-1cew eee eee ciate rereiete II 
Heat, specific. See specific heat. 
Heat, utilization of unavailable .. .72 


Helium, liquefaction of Dewar’s... 281 
Helium, separation of, Dewar’s, 


275-276 


Kinetic Cher sy Mia satan canteese 
1-Ghael olen ye Solace Steen wan aicin eee 204 
Laboratory liquid air apparatus, 
Lindes! tease A ee ice AC el 
Latent Heat <3. co dew sls eeetneee te 2a 
Ta ToursCagniard des. ene OT 2Oe 
La Tour’s law... . ..20-21, 128-129 
Lavoisier ne: ..asGee Higiwins wee OR 


Taw, La “DOUrl’S wees efasarices eens 
ayer, Crookes icy. nae . 80-82 


Leyden University, Cailletet’s 
piUInip in... ij lesenteweeieas Palos 

Leyden University, Pictet’ s cycles 
ieee: Sthundaishe L5G LS 


Liebig’s abet of aceidoue with 
Thilorier’s apparatus....... 138-139 


INDEX. 


Linde.....226, 238, 265, 300, 301, 307- 
319, 322 

Linde’s liquefaction process and 
AV PATAlUS,.. cies cetenge~! Po 307-319 

Liquefaction in tubes, Davy’s sug- 
SeSLIOMsLOL Me wecieeree ey ire 126-127 

Liquefaction of gases, Faraday’s 
Pest awohs= Oly, 2 tees PLOOMLTO 

Liquefaction of hydrogen, Pictet’s 
experimentin «... . 164-165 

Liquefaction process and appara- 


ENG SALLITELS Ge ne Nee ore 307-319 
Liquefied gas receiver, Caille- 

EUS TR ca rae one cata . 195-196 
Liquid air accelerating combus- 

RAIN Ba oe Aeeten WOM Meee ee 332-333 


Liquid air r apparatus, Linders 309-312 
Liquid air as source of oxygen.316-318 
Liquid air as source of power......356 
Liquid air defined........ 69) 
Liquid air dropped into mater pane 
Liquid air, experiments with. .325-337 


Liquid air explosive.... .. 0348-353 
Liquid air, filtering..... pure nert a 20=3 27, 
Liquid air, gasification of........ rg 2 
Liquid air giving two liquids.... 220 
Liquid air in Dewar bulb....... eso 
*haquid airan flask £.\..22..< an 53 
Liquid air, medical uses of ....342-343 
aquade Pictets ca. cae. snack 24, 169-171 
( Liquid floating on a gas......see. wei! 
Liquid fluorine, data of.... . ... 278-280 
Liquid helium, Dewar’s produc- 
tion of THUR relosicerstete r roe col 
Piquidihy drogenintses ar . . 280-285 
Liquid hydrogen, data of...... 280-283 


Liquid hydrogen, Olszewski’s de- 
termination of constant of .227-229 
Liquids and solids, solutions of, 


TASES Meet ee ee My ct  Oay 23-24 
Liquids, molecular motionin..... apes) 
Liquid'state: 2 .....3% desubootudcdssc vel 
Liveing, G.D. w oete/al ele aie's' «wis ieiere es 232 
ANAS LOLCE LSS cr tyacm ees «oe ie ere tone 29 
Low temperatures, applications 

Oy then Tole ee oe ECON ee . .338-356 
Machinery, Dewar’s, Royal Insti- 

RUC ate Ais. fae to Sif aeRO Ox 239 
Magnetism of oxygen...... .. aay 
Manometer, Faraday’s.......,.124-125 


Manometers, Cailletet’s,.......187-189 


363 


Marsh gas, liquid, as refrigerant..215 


WRA SS Aare eter trea s Ate iretin.. a ledereaiaiotele eee 
Matter, icritical staterof, 5 .6c%i5- 19-20 
Matter, three forms or states of. .. 11 


Maxwell, J. Clerk. ....150, 204, 225, 289 
Maxwell, J. Clerk, on low grade 


NEAMEHera Verne he ee Sees 289 
Medical uses of liquid air...... 342-343 
Meniscus defined ... Beit cathe ae 21 
Mercury frozen by liquid air... 331-332 
Mercury vapor, experiment in 

PUCeZIT haan ere er, 253-254 


Metals affected: by iatense cold,.328-329 

Metals, effect of intense cold on 
elaSlicity, 0 tae el 255-256, 260 

Metals, effect of intense cold on 


elon Sationioteanee eae 259-260 
Metals, effect of intense cold on 

Strencthyoigse. aie eee 256-259 
Metals, Tresca’s flow of........ 255 256 
Mixtures ENiOrien Se ieds.cccsne ot 113 
Moissaun and Dewar’s liquefaction 

(on ishblevmnuvs: AP pen) Le . .276-280 
IMOISsatin PLOle ener 2320277) 
Molecular attraction.............II-12 
Molecular death... ..t.... HAPRaE Re es eis doy 
Molecular motion of gases...... .17-18 
Molecular motion of solids...,......11 
Mond yer, Ludwis ines seen eal 
Monge and Clouet......... boat .IIO 
Natterer, J..19, 42, 141-147, 169, 194, 


2URI2L3 210 
Natterer’s apparatus and experi- 


SILC MUCH roti dese shednteseemrevers «ers 141-147 
Natterer’s freezing mixture ...... 145 
Natterer sithermometer. 1... atAS Wore 
INALLeEreIy Ste meat er 23. 2135210 
Negative Joule-Thomson effect..... 301 
Nitrogen, anomalies of ........:.... 88. 


Nitrogen, Cailletet’s liquefaction 


Nitrogen dispatch, Wroblewski 
and Olszewski’s 
Nitrogen, solidification of, by 
Wroblewski and Olszewski....214 
Nitrous oxide, Faraday’s liquefac- 
tI OLA 2 aa eee ACK See ELL 
Nitrous oxide, Natterer’s liquefac- 
tionloh 7 Sawer: . 145 
Nitrous iicides ptimeeatid ‘by Bote 
day as cooling-agent ...........114 


304 


Northmore, Thomas, .106, 110, 117- 


ETS wL20 22 et AS 


Northmore, Thomas, liquefac- 
LIONS DY, Ce eis toe OO LL EO 
Onnes, H. Kamerlingh......49, 270, 301 


Olszewski, K..42, 145, I51, 157, 165, 
168, 169, 185, 203-229, 266, 267, 301 
Otszewski’s and Pictet’s appara- - 
US ,GGlectinee emeae eee oc 223 
Olszewski’s determination of con- 
stants of liquid hydrogen. .227-229 
Olszewski’s liquefaction appara- 


tus of 1890...:. ena oi teeea Ree . 221-226 
Olszewski’s liquefaction of hydro- 
Cel aApproximaleseneen notes 221 


Olszewski’s static oxygen..-.. 221-226 
Oxygen, Cailletet’s liquefaction 


Oxygen, critical pressure of, 
Wroblewski and Olszewski’s 
Aeterimination! scene e ee 216-217 

Oxygen, critical temperature of, 
Wroblewski and Olszewski’s 


determination eee 217-218 
Oxygen dispatch, Wroblewski 

and Olszewslals 2 eeere eae 211-212 
Oxygen, Linde’s method for pro- 

ducing... SOTO Ly ec hes 
Oxygen, imapaceen Ole Shenk Sy 


Oxygen, specific Pavia detec! 
mination of, Wroblewski and 
Olszewskils ne ater ae 214 

Paris, Dr. John Ayrton, and Fara- 
Gay gee ee nae SiG Sao ae Gata 107-109 

Perkins’ alleged liquefaction of 


Permanent gases, the six so-called.150 
Pictet, “Raowl.26.22024 T29.5125 A750, 
I5I, I52-171, 185, 192, 200, 205, 

220, 223, 225, 233, 264, 289 

Pictet, honors received by..... ...156 

Pictet’s cycles used by Dewar......233 
Pictet’s cycles praised by Wrob- 


TeWSKi. eee conte ree e+ 205-206 
Pictet’s determination of tempera- 
CULE Ts. cevare ce eto eee ae ee OT, 
Pictet’s Experiment: in cold well, 
340-341 
Pictet’s frigotherapy ....... ..338-342 
Pictet’s Intellectual and Moral 
Philosophtyaen eee os coe 57 


INDEX. 


Pictet’s life and characteér......153-I55 

Pictet’s liquefaction of oxygen 
dispatch... ....cssitaeisls a ghana 

Pictet’s original liquefaction ap- 


PaTatus swale as rere eyo 
Pictet sdiquidi, «eee 24, 169-171 
Pictet’s work, importance of.......168 


Pleischl’s lecture on WNatterer’s 
apparatus .... «++ 6144-146 


eeeceecece 


Pneumatic Institution,......... Apnnce): 

Potential energy...... AP ae Ree: 

Power expended in Linde’ Ss ap- 
PaTracuseeeeees CRU ea tees 316, 318 


Power, liquid air as reservoir of....356 
Pressure affecting state of mat- 


1S Oat see ere ete et . 16-17 
Pressure, critical....... PEE ee i seg 
Pressures, enormous, in Natter- 

et’s ex petitients sey neeee «ge 
Pump, Cailletet’s mercury..... IQI-195 
Puntp, Kataday:S “aa-ea nee pons 
Pump, Pictet}Staaacqaceetee eee 166 
Purification of chemicals by 

Coldum..: saohemeen Sits ctor 344 347 
Purity, critical state test of....343-344 
RAMSAY io cae ence eer Jon pono oe 
Reaumur thermometer scale..38, 44-45 
Regnault’s mercury pump......... 193 
Release, Cailletet’sm eee aero 
Ribard’s local application of in- 

tense coldec. > «as jeee es eee 
Ribeau, George, Faraday’s em- 

ployer: (ses eoree mingonedos ce 


Reseneration of cold.-ewesetan 299 
Royal Institution of England.10, 92-99 
Rumford, Countier.- swe 92-95, 118-119 
Rumford’s, Count, experiment in 
liquefaction of gases. .... .118-119 
Secondaaes. Peon mean Seed idles 
Self-intensive refrigeration........300 
Siemens, William. .... . 299, 300, 301 
Silvered gas bulbs ..... Sin ean 
Skating rinks, Pictet's .... 154-155 
Solid state of matter.......... sav au be 
Solid carbon dioxide and Crookes 
LAYOT oe s'n's sas ssh ptsak es eta . 84 
Solids and liquids, solutions of, 
LEASES. . diss s,chtop ocd e Geese ae 
Solids, flow of “siewscsd.u seuss eee eee 
Solids, vaporization of ... ......15-16 
Solution, gaseous, utilized..........24 


UU 


a.) 


—— 


Ee 


Ee 


INDEX. 


Solution of solids and liquids in 


gases EDO OOO eee 
SOLVAY eersceelen aes a tio arise steer eters 265 
Specific heat at constant volume 

and at constant pressure..... 64-65 
Speciic Meat Atomics, wot een. ee 66 
Specific heat of gases............54-65 
Spheroidal state....... et ae 78-84, 243 
State of matter affected by pres- 

SULC cca sweets eraistes ealO=r7 


State of matter, intermediate.13-14, 20 
State of matter, volume affected 


IDVies easiest ieee maine as or LOL 
Steel burned in liquid air..... ~...334 
Strength of metals affected by 

COld ees oe daaeieers cee ee 256-259 
SUPOMIEY Ely falas cisles See ce Cae 122 


Sulphur dioxide, liquefaction of...110 
Sulphureted hydrogen, liquefac- 


HlOMMOL Pees <c Reis ee oie ELO=T i 
SilcLace tenSio tie wes see. dso cece 78-79 
Thermodynamics, second law of.70-71 
Thermometer, calorimetric.....,..- 58 
Thermometer, eléctric . resist- 

aTiCeM ems eae: eh ATES 


Thermometer, Fahrenheit’s.........39 
Thermometer, gas or air.........44-51 
‘Bhermometerenatterer’ sac...) 2IL 


hhermometer scalesayarn.: ace. 37, 44 
Thermometers, substances for 
fPLLT OR ee ere er es eta ta 6 Meee aT AZ 


Thermometer, thermo-electric...51-54 
Thermometric methods, Caille- 
tetistiia [Sloe geen amen cs ee 2OL—202 
chvorier wes. II2, II3, 137-141, 198, 269 
Thilorier’s apparatus exhibited 
by Faraday.... Katha B= oxalate 19D 
Thilorier’s apparatus, fatal acci- 
dent with). 22.422 138-139, 143,145 
Thilorier’s cold-blast blowpipe, 
I4I, 198 
Thilorier’s experiments........ 137-14a 
Thilorier’s freezing mixture..... I41 
Thilorier’s solid carbon dioxide... .137 
Thomson, Sir William,..........61, 62 
AhoOmSOM, Flint pena ets ays eile si) 
STOMIP SOME Heil) Ali een 2 st.ce eens S 


Torricellian vacuum.. .... 249, 252-253 
FLOUt Cao naar elas. -. eae 22 
‘ltansition phenomena, ,7........ 22-23 
Tresca’s flow of metals......... 255-256 


tiple an dePictetan mame. teeters 296 
Tripler, Chas. BE. .226, 235, 255, 266, 

285, 286-296, 287, 289 
Tripler on low grade heat energy, 


288-289 
Tripler’s apparatus and _  pro- 
CESS Tal ei eat nl aetied oon s 2. . 290-295 
Tripler’s buckets for liquid 
ALT OR i SEA, alia ote: ZOO K 200 
Tripler's Hie. 172% sian oe nahn 287-209 
Tubes, Faraday’s bent.......... 123-128 
Vacuum, a heat insulator,..... 244-246 
Vacuum and air space bulbs, effi- 
CIENCY COM PaLedmesrae. east 247 
Vacuum, Blenkroode’s  experi- 
ment illustrating utility of..... 245 
Vacuum bulbs or vessels ... ..244-254 
Vacuum produced by liquid hy- 
MrOSGiieerce rece a eee tela . . 283-284. 
Wapor a 5 Acinic era OL Oe ae 63-64 
Vaporization of solids.... ....... 15- 16 
Villard pee... ane RS cr etereetts ee 6 235 24 
Volumes, relations of, in change 
OLAS eos ie woes we ee A fag iseZit 
Water and air contrasted .......85-86 
Water, three states of....... dene LI=l3 
Wiateh Val DOs. vacle atsfals\elelolereticisteteiere ts 64 
WWE seaneopmiMe ney  mancdedde nec 339 
Whisky frozen by liquid air....330-331 
Witow Ska ve caiccsncue ore oe 55, 57 
WOOL amass emvecigk te cere een 25, 31-32 
Wroblewski and Olszewski’s ap- 
PALALUS eae see . ..206-211 


Wroblewski and Olszewski’s car- 


bon monoxide dispatch........213 
Wroblewski and  Olszewski’s 
TC TOT ENT GIS Palen yy aeias delet 213 
Wroblewski and Olszewski’s oxy- 
SCUMISPALC Ui Aunt desis oe Z an i 
Wroblewski and Olszewski’s oxy- 
Pen liquetactionmn..tees eee 211-212 
Wroblewski, Sigmund von. ...42, 
145, 151, 157, 165, 168, 203-229, 
266, 301 
Wroblewskis™ifer...6+...- 203-205 
Wroblewski’s liquefaction of hy- 
UTOSSi ne Wem Ge. poke 218-219 
Wroblewski on liquefaction of air.220 
Zambiasi........+. plate, one aysasleie nines 22 
LET Osa DSOLULE Ha fa eer sa: Maes 4Ordle 


Zero of thermometer scales...... 37-38 


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This is an interesting written book, with plenty of good engravings, which are 
a great help in making clear any text, no matter how well written. ‘l'here are over 
five hundred separate items, selected from the author’s observations and the ob- 
servations of others, as well as from the leading mechanical papers. It aboundsin 
handy ways of doing work, commonly called shop kinks, as the title of the book 
implies, and there is enough useful information in the book to repay the outlay 
many times over. The devices shown are all taken from actual practice and the 
name of the shops where they are to be found is given, so there is nothing that can 
be called untried or impracticable in {t. The information imparted by books of 
this class, especially when written by men of long experience, is the most valuable 
that can be obtained, and the intelligent shopman wil! carefully consider the means 
employedin various shops, determine which is best adapted to his particular case, 
and adopt the method that will save the most time and money for their employer. 
No machinist can read it without finding new methods and ideas which will be of 
value to him —Machinery, March, 1896. 


*“A strongly bound cloth book, 400 pages, entitled “Shop Kinks” by that 
living encyclopedia of mechanics, Robert Grimshaw. As might be expected, the 
anthor covers almost every possible subject that could come up in a machine shop. 
The articles are well illustrated, and the different processes clearly explained. 
Mr. Grimshaw is not one of those who think there is nothing known outside of 
himself, butis ever gleaning ‘‘ Kinks’ from other men’s brains. A copy should be 
on the desk of every machinist in a factory repair shop, for the right ‘‘ Kink ” at the 
3 cht time will often prevent the stoppage of a factory.”’— Wade's Fibre and Fabric, 

eb. 15, 1896. 


NORMAN W. HENLEY & CO., PUBLISHERS, 


132 Nassau Street, New York. 


Special circular describing the above sent on request, or we will send copies 
on receipt of the price. 


JUST PUBLISHED. 


The Modern [lachinist, 


BRON USL ER ae 


PRICE, = = - = $2.50. 


Specially Adapted to the Use of Machinists, Apprentices, 
Designers, Engineers and Constructors. 


A practical treatise embracing the most approved methods of modern machine-shop practice, 
embracing the applications of recent improved appliances, tools, and devices for facilitating, duplicating, 
and expediting the construction of machines and their parts. 


A NEW BOOK FROI COVER TO COVER. 


Every illustration in this book represents a new device in machine-shop 
practice, and the engravings have been made specially for it. 


8vo. 322 Pages. 257 Illustrations. Price, $2.50. 


What is said of “The Modern Machinist.” 


This is a new work of merit. Itis on‘‘ Modern Machine Shop Methods,” as its name implies. 

It is thoroughly up to date, was written by one of the best-known and progressive machinists of the day, 
is the modern exponent of the science, and all its subjects are treated according to latest developments. 
In short, the book is new from cover to to cover, and is one that every machinist, apprentice, designer, 
engineer, or constructor should possess.—Screntiric Macuinist, Juty 15th, 1895. 

This book is the most complete treatise ofits kind that has yet come under our observation, and 
contains all that is most modern and approved and of the highest efficiency in machine-shop practice, 
etc., etc.—AGE or STEEL, JUNE, 1895. 

There is nothing experimental or visionary about this book, all devices being in actual use and 
giving good results. It might perhaps be called a compendium of shop methods, showing a variety of 
special tools and appliances which will give new ideas to many mechanics, from the superintendent to 
the man at the bench. It will be found a valuable addition to any library, and will be consulted 
whenever a new or difficult job is to be done.—Macuinery, JuLy, 1895. 


NORMAN W. HENLEY & CO., pustisners, 
132 NASSAU STREET, NEW YORK. 


%* Copies of the above sent prepaid on receipt of price. 


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